diff --git a/updater/blockimg.cpp b/updater/blockimg.cpp
new file mode 100644
index 0000000..258d975
--- /dev/null
+++ b/updater/blockimg.cpp
@@ -0,0 +1,1991 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <ctype.h>
+#include <errno.h>
+#include <dirent.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <linux/fs.h>
+#include <pthread.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/ioctl.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "applypatch/applypatch.h"
+#include "edify/expr.h"
+#include "mincrypt/sha.h"
+#include "minzip/Hash.h"
+#include "updater.h"
+
+#define BLOCKSIZE 4096
+
+// Set this to 0 to interpret 'erase' transfers to mean do a
+// BLKDISCARD ioctl (the normal behavior).  Set to 1 to interpret
+// erase to mean fill the region with zeroes.
+#define DEBUG_ERASE  0
+
+#define STASH_DIRECTORY_BASE "/cache/recovery"
+#define STASH_DIRECTORY_MODE 0700
+#define STASH_FILE_MODE 0600
+
+char* PrintSha1(const uint8_t* digest);
+
+typedef struct {
+    int count;
+    int size;
+    int pos[0];
+} RangeSet;
+
+#define RANGESET_MAX_POINTS \
+    ((int)((INT_MAX / sizeof(int)) - sizeof(RangeSet)))
+
+static RangeSet* parse_range(char* text) {
+    char* save;
+    char* token;
+    int num;
+    long int val;
+    RangeSet* out = NULL;
+    size_t bufsize;
+
+    if (!text) {
+        goto err;
+    }
+
+    token = strtok_r(text, ",", &save);
+
+    if (!token) {
+        goto err;
+    }
+
+    val = strtol(token, NULL, 0);
+
+    if (val < 2 || val > RANGESET_MAX_POINTS) {
+        goto err;
+    } else if (val % 2) {
+        goto err; // must be even
+    }
+
+    num = (int) val;
+    bufsize = sizeof(RangeSet) + num * sizeof(int);
+
+    out = reinterpret_cast<RangeSet*>(malloc(bufsize));
+
+    if (!out) {
+        fprintf(stderr, "failed to allocate range of %zu bytes\n", bufsize);
+        goto err;
+    }
+
+    out->count = num / 2;
+    out->size = 0;
+
+    for (int i = 0; i < num; ++i) {
+        token = strtok_r(NULL, ",", &save);
+
+        if (!token) {
+            goto err;
+        }
+
+        val = strtol(token, NULL, 0);
+
+        if (val < 0 || val > INT_MAX) {
+            goto err;
+        }
+
+        out->pos[i] = (int) val;
+
+        if (i % 2) {
+            if (out->pos[i - 1] >= out->pos[i]) {
+                goto err; // empty or negative range
+            }
+
+            if (out->size > INT_MAX - out->pos[i]) {
+                goto err; // overflow
+            }
+
+            out->size += out->pos[i];
+        } else {
+            if (out->size < 0) {
+                goto err;
+            }
+
+            out->size -= out->pos[i];
+        }
+    }
+
+    if (out->size <= 0) {
+        goto err;
+    }
+
+    return out;
+
+err:
+    fprintf(stderr, "failed to parse range '%s'\n", text ? text : "NULL");
+    exit(1);
+}
+
+static int range_overlaps(RangeSet* r1, RangeSet* r2) {
+    int i, j, r1_0, r1_1, r2_0, r2_1;
+
+    if (!r1 || !r2) {
+        return 0;
+    }
+
+    for (i = 0; i < r1->count; ++i) {
+        r1_0 = r1->pos[i * 2];
+        r1_1 = r1->pos[i * 2 + 1];
+
+        for (j = 0; j < r2->count; ++j) {
+            r2_0 = r2->pos[j * 2];
+            r2_1 = r2->pos[j * 2 + 1];
+
+            if (!(r2_0 >= r1_1 || r1_0 >= r2_1)) {
+                return 1;
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int read_all(int fd, uint8_t* data, size_t size) {
+    size_t so_far = 0;
+    while (so_far < size) {
+        ssize_t r = TEMP_FAILURE_RETRY(read(fd, data+so_far, size-so_far));
+        if (r == -1) {
+            fprintf(stderr, "read failed: %s\n", strerror(errno));
+            return -1;
+        }
+        so_far += r;
+    }
+    return 0;
+}
+
+static int write_all(int fd, const uint8_t* data, size_t size) {
+    size_t written = 0;
+    while (written < size) {
+        ssize_t w = TEMP_FAILURE_RETRY(write(fd, data+written, size-written));
+        if (w == -1) {
+            fprintf(stderr, "write failed: %s\n", strerror(errno));
+            return -1;
+        }
+        written += w;
+    }
+
+    if (fsync(fd) == -1) {
+        fprintf(stderr, "fsync failed: %s\n", strerror(errno));
+        return -1;
+    }
+
+    return 0;
+}
+
+static bool check_lseek(int fd, off64_t offset, int whence) {
+    off64_t rc = TEMP_FAILURE_RETRY(lseek64(fd, offset, whence));
+    if (rc == -1) {
+        fprintf(stderr, "lseek64 failed: %s\n", strerror(errno));
+        return false;
+    }
+    return true;
+}
+
+static void allocate(size_t size, uint8_t** buffer, size_t* buffer_alloc) {
+    // if the buffer's big enough, reuse it.
+    if (size <= *buffer_alloc) return;
+
+    free(*buffer);
+
+    *buffer = (uint8_t*) malloc(size);
+    if (*buffer == NULL) {
+        fprintf(stderr, "failed to allocate %zu bytes\n", size);
+        exit(1);
+    }
+    *buffer_alloc = size;
+}
+
+typedef struct {
+    int fd;
+    RangeSet* tgt;
+    int p_block;
+    size_t p_remain;
+} RangeSinkState;
+
+static ssize_t RangeSinkWrite(const uint8_t* data, ssize_t size, void* token) {
+    RangeSinkState* rss = (RangeSinkState*) token;
+
+    if (rss->p_remain <= 0) {
+        fprintf(stderr, "range sink write overrun");
+        return 0;
+    }
+
+    ssize_t written = 0;
+    while (size > 0) {
+        size_t write_now = size;
+
+        if (rss->p_remain < write_now) {
+            write_now = rss->p_remain;
+        }
+
+        if (write_all(rss->fd, data, write_now) == -1) {
+            break;
+        }
+
+        data += write_now;
+        size -= write_now;
+
+        rss->p_remain -= write_now;
+        written += write_now;
+
+        if (rss->p_remain == 0) {
+            // move to the next block
+            ++rss->p_block;
+            if (rss->p_block < rss->tgt->count) {
+                rss->p_remain = (rss->tgt->pos[rss->p_block * 2 + 1] -
+                                 rss->tgt->pos[rss->p_block * 2]) * BLOCKSIZE;
+
+                if (!check_lseek(rss->fd, (off64_t)rss->tgt->pos[rss->p_block*2] * BLOCKSIZE,
+                                 SEEK_SET)) {
+                    break;
+                }
+            } else {
+                // we can't write any more; return how many bytes have
+                // been written so far.
+                break;
+            }
+        }
+    }
+
+    return written;
+}
+
+// All of the data for all the 'new' transfers is contained in one
+// file in the update package, concatenated together in the order in
+// which transfers.list will need it.  We want to stream it out of the
+// archive (it's compressed) without writing it to a temp file, but we
+// can't write each section until it's that transfer's turn to go.
+//
+// To achieve this, we expand the new data from the archive in a
+// background thread, and block that threads 'receive uncompressed
+// data' function until the main thread has reached a point where we
+// want some new data to be written.  We signal the background thread
+// with the destination for the data and block the main thread,
+// waiting for the background thread to complete writing that section.
+// Then it signals the main thread to wake up and goes back to
+// blocking waiting for a transfer.
+//
+// NewThreadInfo is the struct used to pass information back and forth
+// between the two threads.  When the main thread wants some data
+// written, it sets rss to the destination location and signals the
+// condition.  When the background thread is done writing, it clears
+// rss and signals the condition again.
+
+typedef struct {
+    ZipArchive* za;
+    const ZipEntry* entry;
+
+    RangeSinkState* rss;
+
+    pthread_mutex_t mu;
+    pthread_cond_t cv;
+} NewThreadInfo;
+
+static bool receive_new_data(const unsigned char* data, int size, void* cookie) {
+    NewThreadInfo* nti = (NewThreadInfo*) cookie;
+
+    while (size > 0) {
+        // Wait for nti->rss to be non-NULL, indicating some of this
+        // data is wanted.
+        pthread_mutex_lock(&nti->mu);
+        while (nti->rss == NULL) {
+            pthread_cond_wait(&nti->cv, &nti->mu);
+        }
+        pthread_mutex_unlock(&nti->mu);
+
+        // At this point nti->rss is set, and we own it.  The main
+        // thread is waiting for it to disappear from nti.
+        ssize_t written = RangeSinkWrite(data, size, nti->rss);
+        data += written;
+        size -= written;
+
+        if (nti->rss->p_block == nti->rss->tgt->count) {
+            // we have written all the bytes desired by this rss.
+
+            pthread_mutex_lock(&nti->mu);
+            nti->rss = NULL;
+            pthread_cond_broadcast(&nti->cv);
+            pthread_mutex_unlock(&nti->mu);
+        }
+    }
+
+    return true;
+}
+
+static void* unzip_new_data(void* cookie) {
+    NewThreadInfo* nti = (NewThreadInfo*) cookie;
+    mzProcessZipEntryContents(nti->za, nti->entry, receive_new_data, nti);
+    return NULL;
+}
+
+static int ReadBlocks(RangeSet* src, uint8_t* buffer, int fd) {
+    int i;
+    size_t p = 0;
+    size_t size;
+
+    if (!src || !buffer) {
+        return -1;
+    }
+
+    for (i = 0; i < src->count; ++i) {
+        if (!check_lseek(fd, (off64_t) src->pos[i * 2] * BLOCKSIZE, SEEK_SET)) {
+            return -1;
+        }
+
+        size = (src->pos[i * 2 + 1] - src->pos[i * 2]) * BLOCKSIZE;
+
+        if (read_all(fd, buffer + p, size) == -1) {
+            return -1;
+        }
+
+        p += size;
+    }
+
+    return 0;
+}
+
+static int WriteBlocks(RangeSet* tgt, uint8_t* buffer, int fd) {
+    int i;
+    size_t p = 0;
+    size_t size;
+
+    if (!tgt || !buffer) {
+        return -1;
+    }
+
+    for (i = 0; i < tgt->count; ++i) {
+        if (!check_lseek(fd, (off64_t) tgt->pos[i * 2] * BLOCKSIZE, SEEK_SET)) {
+            return -1;
+        }
+
+        size = (tgt->pos[i * 2 + 1] - tgt->pos[i * 2]) * BLOCKSIZE;
+
+        if (write_all(fd, buffer + p, size) == -1) {
+            return -1;
+        }
+
+        p += size;
+    }
+
+    return 0;
+}
+
+// Do a source/target load for move/bsdiff/imgdiff in version 1.
+// 'wordsave' is the save_ptr of a strtok_r()-in-progress.  We expect
+// to parse the remainder of the string as:
+//
+//    <src_range> <tgt_range>
+//
+// The source range is loaded into the provided buffer, reallocating
+// it to make it larger if necessary.  The target ranges are returned
+// in *tgt, if tgt is non-NULL.
+
+static int LoadSrcTgtVersion1(char** wordsave, RangeSet** tgt, int* src_blocks,
+                               uint8_t** buffer, size_t* buffer_alloc, int fd) {
+    char* word;
+    int rc;
+
+    word = strtok_r(NULL, " ", wordsave);
+    RangeSet* src = parse_range(word);
+
+    if (tgt != NULL) {
+        word = strtok_r(NULL, " ", wordsave);
+        *tgt = parse_range(word);
+    }
+
+    allocate(src->size * BLOCKSIZE, buffer, buffer_alloc);
+    rc = ReadBlocks(src, *buffer, fd);
+    *src_blocks = src->size;
+
+    free(src);
+    return rc;
+}
+
+static int VerifyBlocks(const char *expected, const uint8_t *buffer,
+                        size_t blocks, int printerror) {
+    char* hexdigest = NULL;
+    int rc = -1;
+    uint8_t digest[SHA_DIGEST_SIZE];
+
+    if (!expected || !buffer) {
+        return rc;
+    }
+
+    SHA_hash(buffer, blocks * BLOCKSIZE, digest);
+    hexdigest = PrintSha1(digest);
+
+    if (hexdigest != NULL) {
+        rc = strcmp(expected, hexdigest);
+
+        if (rc != 0 && printerror) {
+            fprintf(stderr, "failed to verify blocks (expected %s, read %s)\n",
+                expected, hexdigest);
+        }
+
+        free(hexdigest);
+    }
+
+    return rc;
+}
+
+static char* GetStashFileName(const char* base, const char* id, const char* postfix) {
+    char* fn;
+    int len;
+    int res;
+
+    if (base == NULL) {
+        return NULL;
+    }
+
+    if (id == NULL) {
+        id = "";
+    }
+
+    if (postfix == NULL) {
+        postfix = "";
+    }
+
+    len = strlen(STASH_DIRECTORY_BASE) + 1 + strlen(base) + 1 + strlen(id) + strlen(postfix) + 1;
+    fn = reinterpret_cast<char*>(malloc(len));
+
+    if (fn == NULL) {
+        fprintf(stderr, "failed to malloc %d bytes for fn\n", len);
+        return NULL;
+    }
+
+    res = snprintf(fn, len, STASH_DIRECTORY_BASE "/%s/%s%s", base, id, postfix);
+
+    if (res < 0 || res >= len) {
+        fprintf(stderr, "failed to format file name (return value %d)\n", res);
+        free(fn);
+        return NULL;
+    }
+
+    return fn;
+}
+
+typedef void (*StashCallback)(const char*, void*);
+
+// Does a best effort enumeration of stash files. Ignores possible non-file
+// items in the stash directory and continues despite of errors. Calls the
+// 'callback' function for each file and passes 'data' to the function as a
+// parameter.
+
+static void EnumerateStash(const char* dirname, StashCallback callback, void* data) {
+    char* fn;
+    DIR* directory;
+    int len;
+    int res;
+    struct dirent* item;
+
+    if (dirname == NULL || callback == NULL) {
+        return;
+    }
+
+    directory = opendir(dirname);
+
+    if (directory == NULL) {
+        if (errno != ENOENT) {
+            fprintf(stderr, "opendir \"%s\" failed: %s\n", dirname, strerror(errno));
+        }
+        return;
+    }
+
+    while ((item = readdir(directory)) != NULL) {
+        if (item->d_type != DT_REG) {
+            continue;
+        }
+
+        len = strlen(dirname) + 1 + strlen(item->d_name) + 1;
+        fn = reinterpret_cast<char*>(malloc(len));
+
+        if (fn == NULL) {
+            fprintf(stderr, "failed to malloc %d bytes for fn\n", len);
+            continue;
+        }
+
+        res = snprintf(fn, len, "%s/%s", dirname, item->d_name);
+
+        if (res < 0 || res >= len) {
+            fprintf(stderr, "failed to format file name (return value %d)\n", res);
+            free(fn);
+            continue;
+        }
+
+        callback(fn, data);
+        free(fn);
+    }
+
+    if (closedir(directory) == -1) {
+        fprintf(stderr, "closedir \"%s\" failed: %s\n", dirname, strerror(errno));
+    }
+}
+
+static void UpdateFileSize(const char* fn, void* data) {
+    int* size = (int*) data;
+    struct stat st;
+
+    if (!fn || !data) {
+        return;
+    }
+
+    if (stat(fn, &st) == -1) {
+        fprintf(stderr, "stat \"%s\" failed: %s\n", fn, strerror(errno));
+        return;
+    }
+
+    *size += st.st_size;
+}
+
+// Deletes the stash directory and all files in it. Assumes that it only
+// contains files. There is nothing we can do about unlikely, but possible
+// errors, so they are merely logged.
+
+static void DeleteFile(const char* fn, void* data) {
+    if (fn) {
+        fprintf(stderr, "deleting %s\n", fn);
+
+        if (unlink(fn) == -1 && errno != ENOENT) {
+            fprintf(stderr, "unlink \"%s\" failed: %s\n", fn, strerror(errno));
+        }
+    }
+}
+
+static void DeletePartial(const char* fn, void* data) {
+    if (fn && strstr(fn, ".partial") != NULL) {
+        DeleteFile(fn, data);
+    }
+}
+
+static void DeleteStash(const char* base) {
+    char* dirname;
+
+    if (base == NULL) {
+        return;
+    }
+
+    dirname = GetStashFileName(base, NULL, NULL);
+
+    if (dirname == NULL) {
+        return;
+    }
+
+    fprintf(stderr, "deleting stash %s\n", base);
+    EnumerateStash(dirname, DeleteFile, NULL);
+
+    if (rmdir(dirname) == -1) {
+        if (errno != ENOENT && errno != ENOTDIR) {
+            fprintf(stderr, "rmdir \"%s\" failed: %s\n", dirname, strerror(errno));
+        }
+    }
+
+    free(dirname);
+}
+
+static int LoadStash(const char* base, const char* id, int verify, int* blocks, uint8_t** buffer,
+        size_t* buffer_alloc, int printnoent) {
+    char *fn = NULL;
+    int blockcount = 0;
+    int fd = -1;
+    int rc = -1;
+    int res;
+    struct stat st;
+
+    if (!base || !id || !buffer || !buffer_alloc) {
+        goto lsout;
+    }
+
+    if (!blocks) {
+        blocks = &blockcount;
+    }
+
+    fn = GetStashFileName(base, id, NULL);
+
+    if (fn == NULL) {
+        goto lsout;
+    }
+
+    res = stat(fn, &st);
+
+    if (res == -1) {
+        if (errno != ENOENT || printnoent) {
+            fprintf(stderr, "stat \"%s\" failed: %s\n", fn, strerror(errno));
+        }
+        goto lsout;
+    }
+
+    fprintf(stderr, " loading %s\n", fn);
+
+    if ((st.st_size % BLOCKSIZE) != 0) {
+        fprintf(stderr, "%s size %" PRId64 " not multiple of block size %d",
+                fn, static_cast<int64_t>(st.st_size), BLOCKSIZE);
+        goto lsout;
+    }
+
+    fd = TEMP_FAILURE_RETRY(open(fn, O_RDONLY));
+
+    if (fd == -1) {
+        fprintf(stderr, "open \"%s\" failed: %s\n", fn, strerror(errno));
+        goto lsout;
+    }
+
+    allocate(st.st_size, buffer, buffer_alloc);
+
+    if (read_all(fd, *buffer, st.st_size) == -1) {
+        goto lsout;
+    }
+
+    *blocks = st.st_size / BLOCKSIZE;
+
+    if (verify && VerifyBlocks(id, *buffer, *blocks, 1) != 0) {
+        fprintf(stderr, "unexpected contents in %s\n", fn);
+        DeleteFile(fn, NULL);
+        goto lsout;
+    }
+
+    rc = 0;
+
+lsout:
+    if (fd != -1) {
+        close(fd);
+    }
+
+    if (fn) {
+        free(fn);
+    }
+
+    return rc;
+}
+
+static int WriteStash(const char* base, const char* id, int blocks, uint8_t* buffer,
+        int checkspace, int *exists) {
+    char *fn = NULL;
+    char *cn = NULL;
+    int fd = -1;
+    int rc = -1;
+    int res;
+    struct stat st;
+
+    if (base == NULL || buffer == NULL) {
+        goto wsout;
+    }
+
+    if (checkspace && CacheSizeCheck(blocks * BLOCKSIZE) != 0) {
+        fprintf(stderr, "not enough space to write stash\n");
+        goto wsout;
+    }
+
+    fn = GetStashFileName(base, id, ".partial");
+    cn = GetStashFileName(base, id, NULL);
+
+    if (fn == NULL || cn == NULL) {
+        goto wsout;
+    }
+
+    if (exists) {
+        res = stat(cn, &st);
+
+        if (res == 0) {
+            // The file already exists and since the name is the hash of the contents,
+            // it's safe to assume the contents are identical (accidental hash collisions
+            // are unlikely)
+            fprintf(stderr, " skipping %d existing blocks in %s\n", blocks, cn);
+            *exists = 1;
+            rc = 0;
+            goto wsout;
+        }
+
+        *exists = 0;
+    }
+
+    fprintf(stderr, " writing %d blocks to %s\n", blocks, cn);
+
+    fd = TEMP_FAILURE_RETRY(open(fn, O_WRONLY | O_CREAT | O_TRUNC | O_SYNC, STASH_FILE_MODE));
+
+    if (fd == -1) {
+        fprintf(stderr, "failed to create \"%s\": %s\n", fn, strerror(errno));
+        goto wsout;
+    }
+
+    if (write_all(fd, buffer, blocks * BLOCKSIZE) == -1) {
+        goto wsout;
+    }
+
+    if (fsync(fd) == -1) {
+        fprintf(stderr, "fsync \"%s\" failed: %s\n", fn, strerror(errno));
+        goto wsout;
+    }
+
+    if (rename(fn, cn) == -1) {
+        fprintf(stderr, "rename(\"%s\", \"%s\") failed: %s\n", fn, cn, strerror(errno));
+        goto wsout;
+    }
+
+    rc = 0;
+
+wsout:
+    if (fd != -1) {
+        close(fd);
+    }
+
+    if (fn) {
+        free(fn);
+    }
+
+    if (cn) {
+        free(cn);
+    }
+
+    return rc;
+}
+
+// Creates a directory for storing stash files and checks if the /cache partition
+// hash enough space for the expected amount of blocks we need to store. Returns
+// >0 if we created the directory, zero if it existed already, and <0 of failure.
+
+static int CreateStash(State* state, int maxblocks, const char* blockdev, char** base) {
+    char* dirname = NULL;
+    const uint8_t* digest;
+    int rc = -1;
+    int res;
+    int size = 0;
+    SHA_CTX ctx;
+    struct stat st;
+
+    if (blockdev == NULL || base == NULL) {
+        goto csout;
+    }
+
+    // Stash directory should be different for each partition to avoid conflicts
+    // when updating multiple partitions at the same time, so we use the hash of
+    // the block device name as the base directory
+    SHA_init(&ctx);
+    SHA_update(&ctx, blockdev, strlen(blockdev));
+    digest = SHA_final(&ctx);
+    *base = PrintSha1(digest);
+
+    if (*base == NULL) {
+        goto csout;
+    }
+
+    dirname = GetStashFileName(*base, NULL, NULL);
+
+    if (dirname == NULL) {
+        goto csout;
+    }
+
+    res = stat(dirname, &st);
+
+    if (res == -1 && errno != ENOENT) {
+        ErrorAbort(state, "stat \"%s\" failed: %s\n", dirname, strerror(errno));
+        goto csout;
+    } else if (res != 0) {
+        fprintf(stderr, "creating stash %s\n", dirname);
+        res = mkdir(dirname, STASH_DIRECTORY_MODE);
+
+        if (res != 0) {
+            ErrorAbort(state, "mkdir \"%s\" failed: %s\n", dirname, strerror(errno));
+            goto csout;
+        }
+
+        if (CacheSizeCheck(maxblocks * BLOCKSIZE) != 0) {
+            ErrorAbort(state, "not enough space for stash\n");
+            goto csout;
+        }
+
+        rc = 1; // Created directory
+        goto csout;
+    }
+
+    fprintf(stderr, "using existing stash %s\n", dirname);
+
+    // If the directory already exists, calculate the space already allocated to
+    // stash files and check if there's enough for all required blocks. Delete any
+    // partially completed stash files first.
+
+    EnumerateStash(dirname, DeletePartial, NULL);
+    EnumerateStash(dirname, UpdateFileSize, &size);
+
+    size = (maxblocks * BLOCKSIZE) - size;
+
+    if (size > 0 && CacheSizeCheck(size) != 0) {
+        ErrorAbort(state, "not enough space for stash (%d more needed)\n", size);
+        goto csout;
+    }
+
+    rc = 0; // Using existing directory
+
+csout:
+    if (dirname) {
+        free(dirname);
+    }
+
+    return rc;
+}
+
+static int SaveStash(const char* base, char** wordsave, uint8_t** buffer, size_t* buffer_alloc,
+                      int fd, int usehash, int* isunresumable) {
+    char *id = NULL;
+    int blocks = 0;
+
+    if (!wordsave || !buffer || !buffer_alloc || !isunresumable) {
+        return -1;
+    }
+
+    id = strtok_r(NULL, " ", wordsave);
+
+    if (id == NULL) {
+        fprintf(stderr, "missing id field in stash command\n");
+        return -1;
+    }
+
+    if (usehash && LoadStash(base, id, 1, &blocks, buffer, buffer_alloc, 0) == 0) {
+        // Stash file already exists and has expected contents. Do not
+        // read from source again, as the source may have been already
+        // overwritten during a previous attempt.
+        return 0;
+    }
+
+    if (LoadSrcTgtVersion1(wordsave, NULL, &blocks, buffer, buffer_alloc, fd) == -1) {
+        return -1;
+    }
+
+    if (usehash && VerifyBlocks(id, *buffer, blocks, 1) != 0) {
+        // Source blocks have unexpected contents. If we actually need this
+        // data later, this is an unrecoverable error. However, the command
+        // that uses the data may have already completed previously, so the
+        // possible failure will occur during source block verification.
+        fprintf(stderr, "failed to load source blocks for stash %s\n", id);
+        return 0;
+    }
+
+    fprintf(stderr, "stashing %d blocks to %s\n", blocks, id);
+    return WriteStash(base, id, blocks, *buffer, 0, NULL);
+}
+
+static int FreeStash(const char* base, const char* id) {
+    char *fn = NULL;
+
+    if (base == NULL || id == NULL) {
+        return -1;
+    }
+
+    fn = GetStashFileName(base, id, NULL);
+
+    if (fn == NULL) {
+        return -1;
+    }
+
+    DeleteFile(fn, NULL);
+    free(fn);
+
+    return 0;
+}
+
+static void MoveRange(uint8_t* dest, RangeSet* locs, const uint8_t* source) {
+    // source contains packed data, which we want to move to the
+    // locations given in *locs in the dest buffer.  source and dest
+    // may be the same buffer.
+
+    int start = locs->size;
+    int i;
+    for (i = locs->count-1; i >= 0; --i) {
+        int blocks = locs->pos[i*2+1] - locs->pos[i*2];
+        start -= blocks;
+        memmove(dest + (locs->pos[i*2] * BLOCKSIZE), source + (start * BLOCKSIZE),
+                blocks * BLOCKSIZE);
+    }
+}
+
+// Do a source/target load for move/bsdiff/imgdiff in version 2.
+// 'wordsave' is the save_ptr of a strtok_r()-in-progress.  We expect
+// to parse the remainder of the string as one of:
+//
+//    <tgt_range> <src_block_count> <src_range>
+//        (loads data from source image only)
+//
+//    <tgt_range> <src_block_count> - <[stash_id:stash_range] ...>
+//        (loads data from stashes only)
+//
+//    <tgt_range> <src_block_count> <src_range> <src_loc> <[stash_id:stash_range] ...>
+//        (loads data from both source image and stashes)
+//
+// On return, buffer is filled with the loaded source data (rearranged
+// and combined with stashed data as necessary).  buffer may be
+// reallocated if needed to accommodate the source data.  *tgt is the
+// target RangeSet.  Any stashes required are loaded using LoadStash.
+
+static int LoadSrcTgtVersion2(char** wordsave, RangeSet** tgt, int* src_blocks,
+                               uint8_t** buffer, size_t* buffer_alloc, int fd,
+                               const char* stashbase, int* overlap) {
+    char* word;
+    char* colonsave;
+    char* colon;
+    int res;
+    RangeSet* locs;
+    size_t stashalloc = 0;
+    uint8_t* stash = NULL;
+
+    if (tgt != NULL) {
+        word = strtok_r(NULL, " ", wordsave);
+        *tgt = parse_range(word);
+    }
+
+    word = strtok_r(NULL, " ", wordsave);
+    *src_blocks = strtol(word, NULL, 0);
+
+    allocate(*src_blocks * BLOCKSIZE, buffer, buffer_alloc);
+
+    word = strtok_r(NULL, " ", wordsave);
+    if (word[0] == '-' && word[1] == '\0') {
+        // no source ranges, only stashes
+    } else {
+        RangeSet* src = parse_range(word);
+        res = ReadBlocks(src, *buffer, fd);
+
+        if (overlap && tgt) {
+            *overlap = range_overlaps(src, *tgt);
+        }
+
+        free(src);
+
+        if (res == -1) {
+            return -1;
+        }
+
+        word = strtok_r(NULL, " ", wordsave);
+        if (word == NULL) {
+            // no stashes, only source range
+            return 0;
+        }
+
+        locs = parse_range(word);
+        MoveRange(*buffer, locs, *buffer);
+        free(locs);
+    }
+
+    while ((word = strtok_r(NULL, " ", wordsave)) != NULL) {
+        // Each word is a an index into the stash table, a colon, and
+        // then a rangeset describing where in the source block that
+        // stashed data should go.
+        colonsave = NULL;
+        colon = strtok_r(word, ":", &colonsave);
+
+        res = LoadStash(stashbase, colon, 0, NULL, &stash, &stashalloc, 1);
+
+        if (res == -1) {
+            // These source blocks will fail verification if used later, but we
+            // will let the caller decide if this is a fatal failure
+            fprintf(stderr, "failed to load stash %s\n", colon);
+            continue;
+        }
+
+        colon = strtok_r(NULL, ":", &colonsave);
+        locs = parse_range(colon);
+
+        MoveRange(*buffer, locs, stash);
+        free(locs);
+    }
+
+    if (stash) {
+        free(stash);
+    }
+
+    return 0;
+}
+
+// Parameters for transfer list command functions
+typedef struct {
+    char* cmdname;
+    char* cpos;
+    char* freestash;
+    char* stashbase;
+    int canwrite;
+    int createdstash;
+    int fd;
+    int foundwrites;
+    int isunresumable;
+    int version;
+    int written;
+    NewThreadInfo nti;
+    pthread_t thread;
+    size_t bufsize;
+    uint8_t* buffer;
+    uint8_t* patch_start;
+} CommandParameters;
+
+// Do a source/target load for move/bsdiff/imgdiff in version 3.
+//
+// Parameters are the same as for LoadSrcTgtVersion2, except for 'onehash', which
+// tells the function whether to expect separate source and targe block hashes, or
+// if they are both the same and only one hash should be expected, and
+// 'isunresumable', which receives a non-zero value if block verification fails in
+// a way that the update cannot be resumed anymore.
+//
+// If the function is unable to load the necessary blocks or their contents don't
+// match the hashes, the return value is -1 and the command should be aborted.
+//
+// If the return value is 1, the command has already been completed according to
+// the contents of the target blocks, and should not be performed again.
+//
+// If the return value is 0, source blocks have expected content and the command
+// can be performed.
+
+static int LoadSrcTgtVersion3(CommandParameters* params, RangeSet** tgt, int* src_blocks,
+                              int onehash, int* overlap) {
+    char* srchash = NULL;
+    char* tgthash = NULL;
+    int stash_exists = 0;
+    int rc = -1;
+    uint8_t* tgtbuffer = NULL;
+
+    if (!params|| !tgt || !src_blocks || !overlap) {
+        goto v3out;
+    }
+
+    srchash = strtok_r(NULL, " ", &params->cpos);
+
+    if (srchash == NULL) {
+        fprintf(stderr, "missing source hash\n");
+        goto v3out;
+    }
+
+    if (onehash) {
+        tgthash = srchash;
+    } else {
+        tgthash = strtok_r(NULL, " ", &params->cpos);
+
+        if (tgthash == NULL) {
+            fprintf(stderr, "missing target hash\n");
+            goto v3out;
+        }
+    }
+
+    if (LoadSrcTgtVersion2(&params->cpos, tgt, src_blocks, &params->buffer, &params->bufsize,
+            params->fd, params->stashbase, overlap) == -1) {
+        goto v3out;
+    }
+
+    tgtbuffer = (uint8_t*) malloc((*tgt)->size * BLOCKSIZE);
+
+    if (tgtbuffer == NULL) {
+        fprintf(stderr, "failed to allocate %d bytes\n", (*tgt)->size * BLOCKSIZE);
+        goto v3out;
+    }
+
+    if (ReadBlocks(*tgt, tgtbuffer, params->fd) == -1) {
+        goto v3out;
+    }
+
+    if (VerifyBlocks(tgthash, tgtbuffer, (*tgt)->size, 0) == 0) {
+        // Target blocks already have expected content, command should be skipped
+        rc = 1;
+        goto v3out;
+    }
+
+    if (VerifyBlocks(srchash, params->buffer, *src_blocks, 1) == 0) {
+        // If source and target blocks overlap, stash the source blocks so we can
+        // resume from possible write errors
+        if (*overlap) {
+            fprintf(stderr, "stashing %d overlapping blocks to %s\n", *src_blocks,
+                srchash);
+
+            if (WriteStash(params->stashbase, srchash, *src_blocks, params->buffer, 1,
+                    &stash_exists) != 0) {
+                fprintf(stderr, "failed to stash overlapping source blocks\n");
+                goto v3out;
+            }
+
+            // Can be deleted when the write has completed
+            if (!stash_exists) {
+                params->freestash = srchash;
+            }
+        }
+
+        // Source blocks have expected content, command can proceed
+        rc = 0;
+        goto v3out;
+    }
+
+    if (*overlap && LoadStash(params->stashbase, srchash, 1, NULL, &params->buffer,
+                        &params->bufsize, 1) == 0) {
+        // Overlapping source blocks were previously stashed, command can proceed.
+        // We are recovering from an interrupted command, so we don't know if the
+        // stash can safely be deleted after this command.
+        rc = 0;
+        goto v3out;
+    }
+
+    // Valid source data not available, update cannot be resumed
+    fprintf(stderr, "partition has unexpected contents\n");
+    params->isunresumable = 1;
+
+v3out:
+    if (tgtbuffer) {
+        free(tgtbuffer);
+    }
+
+    return rc;
+}
+
+static int PerformCommandMove(CommandParameters* params) {
+    int blocks = 0;
+    int overlap = 0;
+    int rc = -1;
+    int status = 0;
+    RangeSet* tgt = NULL;
+
+    if (!params) {
+        goto pcmout;
+    }
+
+    if (params->version == 1) {
+        status = LoadSrcTgtVersion1(&params->cpos, &tgt, &blocks, &params->buffer,
+                    &params->bufsize, params->fd);
+    } else if (params->version == 2) {
+        status = LoadSrcTgtVersion2(&params->cpos, &tgt, &blocks, &params->buffer,
+                    &params->bufsize, params->fd, params->stashbase, NULL);
+    } else if (params->version >= 3) {
+        status = LoadSrcTgtVersion3(params, &tgt, &blocks, 1, &overlap);
+    }
+
+    if (status == -1) {
+        fprintf(stderr, "failed to read blocks for move\n");
+        goto pcmout;
+    }
+
+    if (status == 0) {
+        params->foundwrites = 1;
+    } else if (params->foundwrites) {
+        fprintf(stderr, "warning: commands executed out of order [%s]\n", params->cmdname);
+    }
+
+    if (params->canwrite) {
+        if (status == 0) {
+            fprintf(stderr, "  moving %d blocks\n", blocks);
+
+            if (WriteBlocks(tgt, params->buffer, params->fd) == -1) {
+                goto pcmout;
+            }
+        } else {
+            fprintf(stderr, "skipping %d already moved blocks\n", blocks);
+        }
+
+    }
+
+    if (params->freestash) {
+        FreeStash(params->stashbase, params->freestash);
+        params->freestash = NULL;
+    }
+
+    params->written += tgt->size;
+    rc = 0;
+
+pcmout:
+    if (tgt) {
+        free(tgt);
+    }
+
+    return rc;
+}
+
+static int PerformCommandStash(CommandParameters* params) {
+    if (!params) {
+        return -1;
+    }
+
+    return SaveStash(params->stashbase, &params->cpos, &params->buffer, &params->bufsize,
+                params->fd, (params->version >= 3), &params->isunresumable);
+}
+
+static int PerformCommandFree(CommandParameters* params) {
+    if (!params) {
+        return -1;
+    }
+
+    if (params->createdstash || params->canwrite) {
+        return FreeStash(params->stashbase, params->cpos);
+    }
+
+    return 0;
+}
+
+static int PerformCommandZero(CommandParameters* params) {
+    char* range = NULL;
+    int i;
+    int j;
+    int rc = -1;
+    RangeSet* tgt = NULL;
+
+    if (!params) {
+        goto pczout;
+    }
+
+    range = strtok_r(NULL, " ", &params->cpos);
+
+    if (range == NULL) {
+        fprintf(stderr, "missing target blocks for zero\n");
+        goto pczout;
+    }
+
+    tgt = parse_range(range);
+
+    fprintf(stderr, "  zeroing %d blocks\n", tgt->size);
+
+    allocate(BLOCKSIZE, &params->buffer, &params->bufsize);
+    memset(params->buffer, 0, BLOCKSIZE);
+
+    if (params->canwrite) {
+        for (i = 0; i < tgt->count; ++i) {
+            if (!check_lseek(params->fd, (off64_t) tgt->pos[i * 2] * BLOCKSIZE, SEEK_SET)) {
+                goto pczout;
+            }
+
+            for (j = tgt->pos[i * 2]; j < tgt->pos[i * 2 + 1]; ++j) {
+                if (write_all(params->fd, params->buffer, BLOCKSIZE) == -1) {
+                    goto pczout;
+                }
+            }
+        }
+    }
+
+    if (params->cmdname[0] == 'z') {
+        // Update only for the zero command, as the erase command will call
+        // this if DEBUG_ERASE is defined.
+        params->written += tgt->size;
+    }
+
+    rc = 0;
+
+pczout:
+    if (tgt) {
+        free(tgt);
+    }
+
+    return rc;
+}
+
+static int PerformCommandNew(CommandParameters* params) {
+    char* range = NULL;
+    int rc = -1;
+    RangeSet* tgt = NULL;
+    RangeSinkState rss;
+
+    if (!params) {
+        goto pcnout;
+    }
+
+    range = strtok_r(NULL, " ", &params->cpos);
+
+    if (range == NULL) {
+        goto pcnout;
+    }
+
+    tgt = parse_range(range);
+
+    if (params->canwrite) {
+        fprintf(stderr, " writing %d blocks of new data\n", tgt->size);
+
+        rss.fd = params->fd;
+        rss.tgt = tgt;
+        rss.p_block = 0;
+        rss.p_remain = (tgt->pos[1] - tgt->pos[0]) * BLOCKSIZE;
+
+        if (!check_lseek(params->fd, (off64_t) tgt->pos[0] * BLOCKSIZE, SEEK_SET)) {
+            goto pcnout;
+        }
+
+        pthread_mutex_lock(&params->nti.mu);
+        params->nti.rss = &rss;
+        pthread_cond_broadcast(&params->nti.cv);
+
+        while (params->nti.rss) {
+            pthread_cond_wait(&params->nti.cv, &params->nti.mu);
+        }
+
+        pthread_mutex_unlock(&params->nti.mu);
+    }
+
+    params->written += tgt->size;
+    rc = 0;
+
+pcnout:
+    if (tgt) {
+        free(tgt);
+    }
+
+    return rc;
+}
+
+static int PerformCommandDiff(CommandParameters* params) {
+    char* logparams = NULL;
+    char* value = NULL;
+    int blocks = 0;
+    int overlap = 0;
+    int rc = -1;
+    int status = 0;
+    RangeSet* tgt = NULL;
+    RangeSinkState rss;
+    size_t len = 0;
+    size_t offset = 0;
+    Value patch_value;
+
+    if (!params) {
+        goto pcdout;
+    }
+
+    logparams = strdup(params->cpos);
+    value = strtok_r(NULL, " ", &params->cpos);
+
+    if (value == NULL) {
+        fprintf(stderr, "missing patch offset for %s\n", params->cmdname);
+        goto pcdout;
+    }
+
+    offset = strtoul(value, NULL, 0);
+
+    value = strtok_r(NULL, " ", &params->cpos);
+
+    if (value == NULL) {
+        fprintf(stderr, "missing patch length for %s\n", params->cmdname);
+        goto pcdout;
+    }
+
+    len = strtoul(value, NULL, 0);
+
+    if (params->version == 1) {
+        status = LoadSrcTgtVersion1(&params->cpos, &tgt, &blocks, &params->buffer,
+                    &params->bufsize, params->fd);
+    } else if (params->version == 2) {
+        status = LoadSrcTgtVersion2(&params->cpos, &tgt, &blocks, &params->buffer,
+                    &params->bufsize, params->fd, params->stashbase, NULL);
+    } else if (params->version >= 3) {
+        status = LoadSrcTgtVersion3(params, &tgt, &blocks, 0, &overlap);
+    }
+
+    if (status == -1) {
+        fprintf(stderr, "failed to read blocks for diff\n");
+        goto pcdout;
+    }
+
+    if (status == 0) {
+        params->foundwrites = 1;
+    } else if (params->foundwrites) {
+        fprintf(stderr, "warning: commands executed out of order [%s]\n", params->cmdname);
+    }
+
+    if (params->canwrite) {
+        if (status == 0) {
+            fprintf(stderr, "patching %d blocks to %d\n", blocks, tgt->size);
+
+            patch_value.type = VAL_BLOB;
+            patch_value.size = len;
+            patch_value.data = (char*) (params->patch_start + offset);
+
+            rss.fd = params->fd;
+            rss.tgt = tgt;
+            rss.p_block = 0;
+            rss.p_remain = (tgt->pos[1] - tgt->pos[0]) * BLOCKSIZE;
+
+            if (!check_lseek(params->fd, (off64_t) tgt->pos[0] * BLOCKSIZE, SEEK_SET)) {
+                goto pcdout;
+            }
+
+            if (params->cmdname[0] == 'i') {      // imgdiff
+                ApplyImagePatch(params->buffer, blocks * BLOCKSIZE, &patch_value,
+                    &RangeSinkWrite, &rss, NULL, NULL);
+            } else {
+                ApplyBSDiffPatch(params->buffer, blocks * BLOCKSIZE, &patch_value,
+                    0, &RangeSinkWrite, &rss, NULL);
+            }
+
+            // We expect the output of the patcher to fill the tgt ranges exactly.
+            if (rss.p_block != tgt->count || rss.p_remain != 0) {
+                fprintf(stderr, "range sink underrun?\n");
+            }
+        } else {
+            fprintf(stderr, "skipping %d blocks already patched to %d [%s]\n",
+                blocks, tgt->size, logparams);
+        }
+    }
+
+    if (params->freestash) {
+        FreeStash(params->stashbase, params->freestash);
+        params->freestash = NULL;
+    }
+
+    params->written += tgt->size;
+    rc = 0;
+
+pcdout:
+    if (logparams) {
+        free(logparams);
+    }
+
+    if (tgt) {
+        free(tgt);
+    }
+
+    return rc;
+}
+
+static int PerformCommandErase(CommandParameters* params) {
+    char* range = NULL;
+    int i;
+    int rc = -1;
+    RangeSet* tgt = NULL;
+    struct stat st;
+    uint64_t blocks[2];
+
+    if (DEBUG_ERASE) {
+        return PerformCommandZero(params);
+    }
+
+    if (!params) {
+        goto pceout;
+    }
+
+    if (fstat(params->fd, &st) == -1) {
+        fprintf(stderr, "failed to fstat device to erase: %s\n", strerror(errno));
+        goto pceout;
+    }
+
+    if (!S_ISBLK(st.st_mode)) {
+        fprintf(stderr, "not a block device; skipping erase\n");
+        goto pceout;
+    }
+
+    range = strtok_r(NULL, " ", &params->cpos);
+
+    if (range == NULL) {
+        fprintf(stderr, "missing target blocks for erase\n");
+        goto pceout;
+    }
+
+    tgt = parse_range(range);
+
+    if (params->canwrite) {
+        fprintf(stderr, " erasing %d blocks\n", tgt->size);
+
+        for (i = 0; i < tgt->count; ++i) {
+            // offset in bytes
+            blocks[0] = tgt->pos[i * 2] * (uint64_t) BLOCKSIZE;
+            // length in bytes
+            blocks[1] = (tgt->pos[i * 2 + 1] - tgt->pos[i * 2]) * (uint64_t) BLOCKSIZE;
+
+            if (ioctl(params->fd, BLKDISCARD, &blocks) == -1) {
+                fprintf(stderr, "BLKDISCARD ioctl failed: %s\n", strerror(errno));
+                goto pceout;
+            }
+        }
+    }
+
+    rc = 0;
+
+pceout:
+    if (tgt) {
+        free(tgt);
+    }
+
+    return rc;
+}
+
+// Definitions for transfer list command functions
+typedef int (*CommandFunction)(CommandParameters*);
+
+typedef struct {
+    const char* name;
+    CommandFunction f;
+} Command;
+
+// CompareCommands and CompareCommandNames are for the hash table
+
+static int CompareCommands(const void* c1, const void* c2) {
+    return strcmp(((const Command*) c1)->name, ((const Command*) c2)->name);
+}
+
+static int CompareCommandNames(const void* c1, const void* c2) {
+    return strcmp(((const Command*) c1)->name, (const char*) c2);
+}
+
+// HashString is used to hash command names for the hash table
+
+static unsigned int HashString(const char *s) {
+    unsigned int hash = 0;
+    if (s) {
+        while (*s) {
+            hash = hash * 33 + *s++;
+        }
+    }
+    return hash;
+}
+
+// args:
+//    - block device (or file) to modify in-place
+//    - transfer list (blob)
+//    - new data stream (filename within package.zip)
+//    - patch stream (filename within package.zip, must be uncompressed)
+
+static Value* PerformBlockImageUpdate(const char* name, State* state, int argc, Expr* argv[],
+            const Command* commands, int cmdcount, int dryrun) {
+
+    char* line = NULL;
+    char* linesave = NULL;
+    char* logcmd = NULL;
+    char* transfer_list = NULL;
+    CommandParameters params;
+    const Command* cmd = NULL;
+    const ZipEntry* new_entry = NULL;
+    const ZipEntry* patch_entry = NULL;
+    FILE* cmd_pipe = NULL;
+    HashTable* cmdht = NULL;
+    int i;
+    int res;
+    int rc = -1;
+    int stash_max_blocks = 0;
+    int total_blocks = 0;
+    pthread_attr_t attr;
+    unsigned int cmdhash;
+    UpdaterInfo* ui = NULL;
+    Value* blockdev_filename = NULL;
+    Value* new_data_fn = NULL;
+    Value* patch_data_fn = NULL;
+    Value* transfer_list_value = NULL;
+    ZipArchive* za = NULL;
+
+    memset(&params, 0, sizeof(params));
+    params.canwrite = !dryrun;
+
+    fprintf(stderr, "performing %s\n", dryrun ? "verification" : "update");
+
+    if (ReadValueArgs(state, argv, 4, &blockdev_filename, &transfer_list_value,
+            &new_data_fn, &patch_data_fn) < 0) {
+        goto pbiudone;
+    }
+
+    if (blockdev_filename->type != VAL_STRING) {
+        ErrorAbort(state, "blockdev_filename argument to %s must be string", name);
+        goto pbiudone;
+    }
+    if (transfer_list_value->type != VAL_BLOB) {
+        ErrorAbort(state, "transfer_list argument to %s must be blob", name);
+        goto pbiudone;
+    }
+    if (new_data_fn->type != VAL_STRING) {
+        ErrorAbort(state, "new_data_fn argument to %s must be string", name);
+        goto pbiudone;
+    }
+    if (patch_data_fn->type != VAL_STRING) {
+        ErrorAbort(state, "patch_data_fn argument to %s must be string", name);
+        goto pbiudone;
+    }
+
+    ui = (UpdaterInfo*) state->cookie;
+
+    if (ui == NULL) {
+        goto pbiudone;
+    }
+
+    cmd_pipe = ui->cmd_pipe;
+    za = ui->package_zip;
+
+    if (cmd_pipe == NULL || za == NULL) {
+        goto pbiudone;
+    }
+
+    patch_entry = mzFindZipEntry(za, patch_data_fn->data);
+
+    if (patch_entry == NULL) {
+        fprintf(stderr, "%s(): no file \"%s\" in package", name, patch_data_fn->data);
+        goto pbiudone;
+    }
+
+    params.patch_start = ui->package_zip_addr + mzGetZipEntryOffset(patch_entry);
+    new_entry = mzFindZipEntry(za, new_data_fn->data);
+
+    if (new_entry == NULL) {
+        fprintf(stderr, "%s(): no file \"%s\" in package", name, new_data_fn->data);
+        goto pbiudone;
+    }
+
+    params.fd = TEMP_FAILURE_RETRY(open(blockdev_filename->data, O_RDWR));
+
+    if (params.fd == -1) {
+        fprintf(stderr, "open \"%s\" failed: %s\n", blockdev_filename->data, strerror(errno));
+        goto pbiudone;
+    }
+
+    if (params.canwrite) {
+        params.nti.za = za;
+        params.nti.entry = new_entry;
+
+        pthread_mutex_init(&params.nti.mu, NULL);
+        pthread_cond_init(&params.nti.cv, NULL);
+        pthread_attr_init(&attr);
+        pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
+
+        int error = pthread_create(&params.thread, &attr, unzip_new_data, &params.nti);
+        if (error != 0) {
+            fprintf(stderr, "pthread_create failed: %s\n", strerror(error));
+            goto pbiudone;
+        }
+    }
+
+    // The data in transfer_list_value is not necessarily null-terminated, so we need
+    // to copy it to a new buffer and add the null that strtok_r will need.
+    transfer_list = reinterpret_cast<char*>(malloc(transfer_list_value->size + 1));
+
+    if (transfer_list == NULL) {
+        fprintf(stderr, "failed to allocate %zd bytes for transfer list\n",
+            transfer_list_value->size + 1);
+        goto pbiudone;
+    }
+
+    memcpy(transfer_list, transfer_list_value->data, transfer_list_value->size);
+    transfer_list[transfer_list_value->size] = '\0';
+
+    // First line in transfer list is the version number
+    line = strtok_r(transfer_list, "\n", &linesave);
+    params.version = strtol(line, NULL, 0);
+
+    if (params.version < 1 || params.version > 3) {
+        fprintf(stderr, "unexpected transfer list version [%s]\n", line);
+        goto pbiudone;
+    }
+
+    fprintf(stderr, "blockimg version is %d\n", params.version);
+
+    // Second line in transfer list is the total number of blocks we expect to write
+    line = strtok_r(NULL, "\n", &linesave);
+    total_blocks = strtol(line, NULL, 0);
+
+    if (total_blocks < 0) {
+        ErrorAbort(state, "unexpected block count [%s]\n", line);
+        goto pbiudone;
+    } else if (total_blocks == 0) {
+        rc = 0;
+        goto pbiudone;
+    }
+
+    if (params.version >= 2) {
+        // Third line is how many stash entries are needed simultaneously
+        line = strtok_r(NULL, "\n", &linesave);
+        fprintf(stderr, "maximum stash entries %s\n", line);
+
+        // Fourth line is the maximum number of blocks that will be stashed simultaneously
+        line = strtok_r(NULL, "\n", &linesave);
+        stash_max_blocks = strtol(line, NULL, 0);
+
+        if (stash_max_blocks < 0) {
+            ErrorAbort(state, "unexpected maximum stash blocks [%s]\n", line);
+            goto pbiudone;
+        }
+
+        if (stash_max_blocks >= 0) {
+            res = CreateStash(state, stash_max_blocks, blockdev_filename->data,
+                    &params.stashbase);
+
+            if (res == -1) {
+                goto pbiudone;
+            }
+
+            params.createdstash = res;
+        }
+    }
+
+    // Build a hash table of the available commands
+    cmdht = mzHashTableCreate(cmdcount, NULL);
+
+    for (i = 0; i < cmdcount; ++i) {
+        cmdhash = HashString(commands[i].name);
+        mzHashTableLookup(cmdht, cmdhash, (void*) &commands[i], CompareCommands, true);
+    }
+
+    // Subsequent lines are all individual transfer commands
+    for (line = strtok_r(NULL, "\n", &linesave); line;
+         line = strtok_r(NULL, "\n", &linesave)) {
+
+        logcmd = strdup(line);
+        params.cmdname = strtok_r(line, " ", &params.cpos);
+
+        if (params.cmdname == NULL) {
+            fprintf(stderr, "missing command [%s]\n", line);
+            goto pbiudone;
+        }
+
+        cmdhash = HashString(params.cmdname);
+        cmd = (const Command*) mzHashTableLookup(cmdht, cmdhash, params.cmdname,
+                                    CompareCommandNames, false);
+
+        if (cmd == NULL) {
+            fprintf(stderr, "unexpected command [%s]\n", params.cmdname);
+            goto pbiudone;
+        }
+
+        if (cmd->f != NULL && cmd->f(&params) == -1) {
+            fprintf(stderr, "failed to execute command [%s]\n",
+                logcmd ? logcmd : params.cmdname);
+            goto pbiudone;
+        }
+
+        if (logcmd) {
+            free(logcmd);
+            logcmd = NULL;
+        }
+
+        if (params.canwrite) {
+            fprintf(cmd_pipe, "set_progress %.4f\n", (double) params.written / total_blocks);
+            fflush(cmd_pipe);
+        }
+    }
+
+    if (params.canwrite) {
+        pthread_join(params.thread, NULL);
+
+        fprintf(stderr, "wrote %d blocks; expected %d\n", params.written, total_blocks);
+        fprintf(stderr, "max alloc needed was %zu\n", params.bufsize);
+
+        // Delete stash only after successfully completing the update, as it
+        // may contain blocks needed to complete the update later.
+        DeleteStash(params.stashbase);
+    } else {
+        fprintf(stderr, "verified partition contents; update may be resumed\n");
+    }
+
+    rc = 0;
+
+pbiudone:
+    if (params.fd != -1) {
+        if (fsync(params.fd) == -1) {
+            fprintf(stderr, "fsync failed: %s\n", strerror(errno));
+        }
+        close(params.fd);
+    }
+
+    if (logcmd) {
+        free(logcmd);
+    }
+
+    if (cmdht) {
+        mzHashTableFree(cmdht);
+    }
+
+    if (params.buffer) {
+        free(params.buffer);
+    }
+
+    if (transfer_list) {
+        free(transfer_list);
+    }
+
+    if (blockdev_filename) {
+        FreeValue(blockdev_filename);
+    }
+
+    if (transfer_list_value) {
+        FreeValue(transfer_list_value);
+    }
+
+    if (new_data_fn) {
+        FreeValue(new_data_fn);
+    }
+
+    if (patch_data_fn) {
+        FreeValue(patch_data_fn);
+    }
+
+    // Only delete the stash if the update cannot be resumed, or it's
+    // a verification run and we created the stash.
+    if (params.isunresumable || (!params.canwrite && params.createdstash)) {
+        DeleteStash(params.stashbase);
+    }
+
+    if (params.stashbase) {
+        free(params.stashbase);
+    }
+
+    return StringValue(rc == 0 ? strdup("t") : strdup(""));
+}
+
+// The transfer list is a text file containing commands to
+// transfer data from one place to another on the target
+// partition.  We parse it and execute the commands in order:
+//
+//    zero [rangeset]
+//      - fill the indicated blocks with zeros
+//
+//    new [rangeset]
+//      - fill the blocks with data read from the new_data file
+//
+//    erase [rangeset]
+//      - mark the given blocks as empty
+//
+//    move <...>
+//    bsdiff <patchstart> <patchlen> <...>
+//    imgdiff <patchstart> <patchlen> <...>
+//      - read the source blocks, apply a patch (or not in the
+//        case of move), write result to target blocks.  bsdiff or
+//        imgdiff specifies the type of patch; move means no patch
+//        at all.
+//
+//        The format of <...> differs between versions 1 and 2;
+//        see the LoadSrcTgtVersion{1,2}() functions for a
+//        description of what's expected.
+//
+//    stash <stash_id> <src_range>
+//      - (version 2+ only) load the given source range and stash
+//        the data in the given slot of the stash table.
+//
+// The creator of the transfer list will guarantee that no block
+// is read (ie, used as the source for a patch or move) after it
+// has been written.
+//
+// In version 2, the creator will guarantee that a given stash is
+// loaded (with a stash command) before it's used in a
+// move/bsdiff/imgdiff command.
+//
+// Within one command the source and target ranges may overlap so
+// in general we need to read the entire source into memory before
+// writing anything to the target blocks.
+//
+// All the patch data is concatenated into one patch_data file in
+// the update package.  It must be stored uncompressed because we
+// memory-map it in directly from the archive.  (Since patches are
+// already compressed, we lose very little by not compressing
+// their concatenation.)
+//
+// In version 3, commands that read data from the partition (i.e.
+// move/bsdiff/imgdiff/stash) have one or more additional hashes
+// before the range parameters, which are used to check if the
+// command has already been completed and verify the integrity of
+// the source data.
+
+Value* BlockImageVerifyFn(const char* name, State* state, int argc, Expr* argv[]) {
+    // Commands which are not tested are set to NULL to skip them completely
+    const Command commands[] = {
+        { "bsdiff",     PerformCommandDiff  },
+        { "erase",      NULL                },
+        { "free",       PerformCommandFree  },
+        { "imgdiff",    PerformCommandDiff  },
+        { "move",       PerformCommandMove  },
+        { "new",        NULL                },
+        { "stash",      PerformCommandStash },
+        { "zero",       NULL                }
+    };
+
+    // Perform a dry run without writing to test if an update can proceed
+    return PerformBlockImageUpdate(name, state, argc, argv, commands,
+                sizeof(commands) / sizeof(commands[0]), 1);
+}
+
+Value* BlockImageUpdateFn(const char* name, State* state, int argc, Expr* argv[]) {
+    const Command commands[] = {
+        { "bsdiff",     PerformCommandDiff  },
+        { "erase",      PerformCommandErase },
+        { "free",       PerformCommandFree  },
+        { "imgdiff",    PerformCommandDiff  },
+        { "move",       PerformCommandMove  },
+        { "new",        PerformCommandNew   },
+        { "stash",      PerformCommandStash },
+        { "zero",       PerformCommandZero  }
+    };
+
+    return PerformBlockImageUpdate(name, state, argc, argv, commands,
+                sizeof(commands) / sizeof(commands[0]), 0);
+}
+
+Value* RangeSha1Fn(const char* name, State* state, int argc, Expr* argv[]) {
+    Value* blockdev_filename;
+    Value* ranges;
+    const uint8_t* digest = NULL;
+    if (ReadValueArgs(state, argv, 2, &blockdev_filename, &ranges) < 0) {
+        return NULL;
+    }
+
+    if (blockdev_filename->type != VAL_STRING) {
+        ErrorAbort(state, "blockdev_filename argument to %s must be string", name);
+        goto done;
+    }
+    if (ranges->type != VAL_STRING) {
+        ErrorAbort(state, "ranges argument to %s must be string", name);
+        goto done;
+    }
+
+    int fd;
+    fd = open(blockdev_filename->data, O_RDWR);
+    if (fd < 0) {
+        ErrorAbort(state, "open \"%s\" failed: %s", blockdev_filename->data, strerror(errno));
+        goto done;
+    }
+
+    RangeSet* rs;
+    rs = parse_range(ranges->data);
+    uint8_t buffer[BLOCKSIZE];
+
+    SHA_CTX ctx;
+    SHA_init(&ctx);
+
+    int i, j;
+    for (i = 0; i < rs->count; ++i) {
+        if (!check_lseek(fd, (off64_t)rs->pos[i*2] * BLOCKSIZE, SEEK_SET)) {
+            ErrorAbort(state, "failed to seek %s: %s", blockdev_filename->data,
+                strerror(errno));
+            goto done;
+        }
+
+        for (j = rs->pos[i*2]; j < rs->pos[i*2+1]; ++j) {
+            if (read_all(fd, buffer, BLOCKSIZE) == -1) {
+                ErrorAbort(state, "failed to read %s: %s", blockdev_filename->data,
+                    strerror(errno));
+                goto done;
+            }
+
+            SHA_update(&ctx, buffer, BLOCKSIZE);
+        }
+    }
+    digest = SHA_final(&ctx);
+    close(fd);
+
+  done:
+    FreeValue(blockdev_filename);
+    FreeValue(ranges);
+    if (digest == NULL) {
+        return StringValue(strdup(""));
+    } else {
+        return StringValue(PrintSha1(digest));
+    }
+}
+
+void RegisterBlockImageFunctions() {
+    RegisterFunction("block_image_verify", BlockImageVerifyFn);
+    RegisterFunction("block_image_update", BlockImageUpdateFn);
+    RegisterFunction("range_sha1", RangeSha1Fn);
+}