diff --git a/applypatch/applypatch.c b/applypatch/applypatch.c
index 60e9e4a..bfb9440 100644
--- a/applypatch/applypatch.c
+++ b/applypatch/applypatch.c
@@ -32,7 +32,7 @@
 #include "edify/expr.h"
 
 static int LoadPartitionContents(const char* filename, FileContents* file);
-static ssize_t FileSink(unsigned char* data, ssize_t len, void* token);
+static ssize_t FileSink(const unsigned char* data, ssize_t len, void* token);
 static int GenerateTarget(FileContents* source_file,
                           const Value* source_patch_value,
                           FileContents* copy_file,
@@ -599,7 +599,7 @@
     return 0;
 }
 
-ssize_t FileSink(unsigned char* data, ssize_t len, void* token) {
+ssize_t FileSink(const unsigned char* data, ssize_t len, void* token) {
     int fd = *(int *)token;
     ssize_t done = 0;
     ssize_t wrote;
@@ -620,7 +620,7 @@
     ssize_t pos;
 } MemorySinkInfo;
 
-ssize_t MemorySink(unsigned char* data, ssize_t len, void* token) {
+ssize_t MemorySink(const unsigned char* data, ssize_t len, void* token) {
     MemorySinkInfo* msi = (MemorySinkInfo*)token;
     if (msi->size - msi->pos < len) {
         return -1;
diff --git a/applypatch/applypatch.h b/applypatch/applypatch.h
index ee54c24..edec848 100644
--- a/applypatch/applypatch.h
+++ b/applypatch/applypatch.h
@@ -40,7 +40,7 @@
 // and use it as the source instead.
 #define CACHE_TEMP_SOURCE "/cache/saved.file"
 
-typedef ssize_t (*SinkFn)(unsigned char*, ssize_t, void*);
+typedef ssize_t (*SinkFn)(const unsigned char*, ssize_t, void*);
 
 // applypatch.c
 int ShowLicenses();
diff --git a/applypatch/bspatch.c b/applypatch/bspatch.c
index 1dc7ab1..b34ec2a 100644
--- a/applypatch/bspatch.c
+++ b/applypatch/bspatch.c
@@ -112,9 +112,7 @@
         printf("short write of output: %d (%s)\n", errno, strerror(errno));
         return 1;
     }
-    if (ctx) {
-        SHA_update(ctx, new_data, new_size);
-    }
+    if (ctx) SHA_update(ctx, new_data, new_size);
     free(new_data);
 
     return 0;
diff --git a/applypatch/imgpatch.c b/applypatch/imgpatch.c
index af4d072..33c4487 100644
--- a/applypatch/imgpatch.c
+++ b/applypatch/imgpatch.c
@@ -95,7 +95,7 @@
                 printf("failed to read chunk %d raw data\n", i);
                 return -1;
             }
-            SHA_update(ctx, patch->data + pos, data_len);
+            if (ctx) SHA_update(ctx, patch->data + pos, data_len);
             if (sink((unsigned char*)patch->data + pos,
                      data_len, token) != data_len) {
                 printf("failed to write chunk %d raw data\n", i);
@@ -217,7 +217,7 @@
                            (long)have);
                     return -1;
                 }
-                SHA_update(ctx, temp_data, have);
+                if (ctx) SHA_update(ctx, temp_data, have);
             } while (ret != Z_STREAM_END);
             deflateEnd(&strm);
 
diff --git a/updater/Android.mk b/updater/Android.mk
index 99b4890..b183c92 100644
--- a/updater/Android.mk
+++ b/updater/Android.mk
@@ -4,6 +4,7 @@
 
 updater_src_files := \
 	install.c \
+	blockimg.c \
 	updater.c
 
 #
diff --git a/updater/blockimg.c b/updater/blockimg.c
new file mode 100644
index 0000000..c442ab2
--- /dev/null
+++ b/updater/blockimg.c
@@ -0,0 +1,631 @@
+/*
+ * 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 <fcntl.h>
+#include <inttypes.h>
+#include <pthread.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.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/DirUtil.h"
+#include "updater.h"
+
+#define BLOCKSIZE 4096
+
+// Set this to 1 to interpret 'erase' transfers to mean do a
+// BLKDISCARD ioctl.  Set to 0 to interpret erase to mean fill the
+// region with zeroes.
+#define DEBUG_ERASE  0
+
+#ifndef BLKDISCARD
+#define BLKDISCARD _IO(0x12,119)
+#endif
+
+char* PrintSha1(const uint8_t* digest);
+
+typedef struct {
+    int count;
+    int size;
+    int pos[0];
+} RangeSet;
+
+static RangeSet* parse_range(char* text) {
+    char* save;
+    int num;
+    num = strtol(strtok_r(text, ",", &save), NULL, 0);
+
+    RangeSet* out = malloc(sizeof(RangeSet) + num * sizeof(int));
+    if (out == NULL) {
+        fprintf(stderr, "failed to allocate range of %d bytes\n",
+                sizeof(RangeSet) + num * sizeof(int));
+        exit(1);
+    }
+    out->count = num / 2;
+    out->size = 0;
+    int i;
+    for (i = 0; i < num; ++i) {
+        out->pos[i] = strtol(strtok_r(NULL, ",", &save), NULL, 0);
+        if (i%2) {
+            out->size += out->pos[i];
+        } else {
+            out->size -= out->pos[i];
+        }
+    }
+
+    return out;
+}
+
+static void readblock(int fd, uint8_t* data, size_t size) {
+    size_t so_far = 0;
+    while (so_far < size) {
+        ssize_t r = read(fd, data+so_far, size-so_far);
+        if (r < 0 && errno != EINTR) {
+            fprintf(stderr, "read failed: %s\n", strerror(errno));
+            return;
+        } else {
+            so_far += r;
+        }
+    }
+}
+
+static void writeblock(int fd, const uint8_t* data, size_t size) {
+    size_t written = 0;
+    while (written < size) {
+        ssize_t w = write(fd, data+written, size-written);
+        if (w < 0 && errno != EINTR) {
+            fprintf(stderr, "write failed: %s\n", strerror(errno));
+            return;
+        } else {
+            written += w;
+        }
+    }
+}
+
+static void check_lseek(int fd, off_t offset, int whence) {
+    while (true) {
+        int ret = lseek(fd, offset, whence);
+        if (ret < 0) {
+            if (errno != EINTR) {
+                fprintf(stderr, "lseek failed: %s\n", strerror(errno));
+                exit(1);
+            }
+        } else {
+            break;
+        }
+    }
+}
+
+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 %d 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");
+        exit(1);
+    }
+
+    ssize_t written = 0;
+    while (size > 0) {
+        size_t write_now = size;
+        if (rss->p_remain < write_now) write_now = rss->p_remain;
+        writeblock(rss->fd, data, write_now);
+        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;
+                check_lseek(rss->fd, rss->tgt->pos[rss->p_block*2] * BLOCKSIZE, SEEK_SET);
+            } else {
+                // we can't write any more; return how many bytes have
+                // been written so far.
+                return written;
+            }
+        }
+    }
+
+    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;
+}
+
+// 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)
+
+Value* BlockImageUpdateFn(const char* name, State* state, int argc, Expr* argv[]) {
+    Value* blockdev_filename;
+    Value* transfer_list;
+    Value* new_data_fn;
+    Value* patch_data_fn;
+    bool success = false;
+
+    if (ReadValueArgs(state, argv, 4, &blockdev_filename, &transfer_list,
+                      &new_data_fn, &patch_data_fn) < 0) {
+        return NULL;
+    }
+
+    if (blockdev_filename->type != VAL_STRING) {
+        ErrorAbort(state, "blockdev_filename argument to %s must be string", name);
+        goto done;
+    }
+    if (transfer_list->type != VAL_BLOB) {
+        ErrorAbort(state, "transfer_list argument to %s must be blob", name);
+        goto done;
+    }
+    if (new_data_fn->type != VAL_STRING) {
+        ErrorAbort(state, "new_data_fn argument to %s must be string", name);
+        goto done;
+    }
+    if (patch_data_fn->type != VAL_STRING) {
+        ErrorAbort(state, "patch_data_fn argument to %s must be string", name);
+        goto done;
+    }
+
+    UpdaterInfo* ui = (UpdaterInfo*)(state->cookie);
+    FILE* cmd_pipe = ui->cmd_pipe;
+
+    ZipArchive* za = ((UpdaterInfo*)(state->cookie))->package_zip;
+
+    const ZipEntry* patch_entry = mzFindZipEntry(za, patch_data_fn->data);
+    if (patch_entry == NULL) {
+        ErrorAbort(state, "%s(): no file \"%s\" in package", name, patch_data_fn->data);
+        goto done;
+    }
+
+    uint8_t* patch_start = ((UpdaterInfo*)(state->cookie))->package_zip_addr +
+        mzGetZipEntryOffset(patch_entry);
+
+    const ZipEntry* new_entry = mzFindZipEntry(za, new_data_fn->data);
+    if (new_entry == NULL) {
+        ErrorAbort(state, "%s(): no file \"%s\" in package", name, new_data_fn->data);
+        goto done;
+    }
+
+    // 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
+    //
+    //    bsdiff patchstart patchlen [src rangeset] [tgt rangeset]
+    //    imgdiff patchstart patchlen [src rangeset] [tgt rangeset]
+    //      - read the source blocks, apply a patch, write result to
+    //        target blocks.  bsdiff or imgdiff specifies the type of
+    //        patch.
+    //
+    //    move [src rangeset] [tgt rangeset]
+    //      - copy data from source blocks to target blocks (no patch
+    //        needed; rangesets are the same size)
+    //
+    //    erase [rangeset]
+    //      - mark the given blocks as empty
+    //
+    // 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.
+    //
+    // 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.)
+
+    pthread_t new_data_thread;
+    NewThreadInfo nti;
+    nti.za = za;
+    nti.entry = new_entry;
+    nti.rss = NULL;
+    pthread_mutex_init(&nti.mu, NULL);
+    pthread_cond_init(&nti.cv, NULL);
+
+    pthread_attr_t attr;
+    pthread_attr_init(&attr);
+    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
+    pthread_create(&new_data_thread, &attr, unzip_new_data, &nti);
+
+    int i, j;
+
+    char* linesave;
+    char* wordsave;
+
+    int fd = open(blockdev_filename->data, O_RDWR);
+    if (fd < 0) {
+        ErrorAbort(state, "failed to open %s: %s", blockdev_filename->data, strerror(errno));
+        goto done;
+    }
+
+    char* line;
+    char* word;
+
+    line = strtok_r(transfer_list->data, "\n", &linesave);
+
+    // first line in transfer list is the version number; currently
+    // there's only version 1.
+    if (strcmp(line, "1") != 0) {
+        ErrorAbort(state, "unexpected transfer list version [%s]\n", line);
+        goto done;
+    }
+
+    // second line in transfer list is the total number of blocks we
+    // expect to write.
+    line = strtok_r(NULL, "\n", &linesave);
+    int total_blocks = strtol(line, NULL, 0);
+    // shouldn't happen, but avoid divide by zero.
+    if (total_blocks == 0) ++total_blocks;
+    int blocks_so_far = 0;
+
+    uint8_t* buffer = NULL;
+    size_t buffer_alloc = 0;
+
+    // third and subsequent lines are all individual transfer commands.
+    for (line = strtok_r(NULL, "\n", &linesave); line;
+         line = strtok_r(NULL, "\n", &linesave)) {
+        char* style;
+        style = strtok_r(line, " ", &wordsave);
+
+        if (strcmp("move", style) == 0) {
+            word = strtok_r(NULL, " ", &wordsave);
+            RangeSet* src = parse_range(word);
+            word = strtok_r(NULL, " ", &wordsave);
+            RangeSet* tgt = parse_range(word);
+
+            printf("  moving %d blocks\n", src->size);
+
+            allocate(src->size * BLOCKSIZE, &buffer, &buffer_alloc);
+            size_t p = 0;
+            for (i = 0; i < src->count; ++i) {
+                check_lseek(fd, src->pos[i*2] * BLOCKSIZE, SEEK_SET);
+                size_t sz = (src->pos[i*2+1] - src->pos[i*2]) * BLOCKSIZE;
+                readblock(fd, buffer+p, sz);
+                p += sz;
+            }
+
+            p = 0;
+            for (i = 0; i < tgt->count; ++i) {
+                check_lseek(fd, tgt->pos[i*2] * BLOCKSIZE, SEEK_SET);
+                size_t sz = (tgt->pos[i*2+1] - tgt->pos[i*2]) * BLOCKSIZE;
+                writeblock(fd, buffer+p, sz);
+                p += sz;
+            }
+
+            blocks_so_far += tgt->size;
+            fprintf(cmd_pipe, "set_progress %.4f\n", (double)blocks_so_far / total_blocks);
+            fflush(cmd_pipe);
+
+            free(src);
+            free(tgt);
+
+        } else if (strcmp("zero", style) == 0 ||
+                   (DEBUG_ERASE && strcmp("erase", style) == 0)) {
+            word = strtok_r(NULL, " ", &wordsave);
+            RangeSet* tgt = parse_range(word);
+
+            printf("  zeroing %d blocks\n", tgt->size);
+
+            allocate(BLOCKSIZE, &buffer, &buffer_alloc);
+            memset(buffer, 0, BLOCKSIZE);
+            for (i = 0; i < tgt->count; ++i) {
+                check_lseek(fd, tgt->pos[i*2] * BLOCKSIZE, SEEK_SET);
+                for (j = tgt->pos[i*2]; j < tgt->pos[i*2+1]; ++j) {
+                    writeblock(fd, buffer, BLOCKSIZE);
+                }
+            }
+
+            if (style[0] == 'z') {   // "zero" but not "erase"
+                blocks_so_far += tgt->size;
+                fprintf(cmd_pipe, "set_progress %.4f\n", (double)blocks_so_far / total_blocks);
+                fflush(cmd_pipe);
+            }
+
+            free(tgt);
+        } else if (strcmp("new", style) == 0) {
+
+            word = strtok_r(NULL, " ", &wordsave);
+            RangeSet* tgt = parse_range(word);
+
+            printf("  writing %d blocks of new data\n", tgt->size);
+
+            RangeSinkState rss;
+            rss.fd = fd;
+            rss.tgt = tgt;
+            rss.p_block = 0;
+            rss.p_remain = (tgt->pos[1] - tgt->pos[0]) * BLOCKSIZE;
+            check_lseek(fd, tgt->pos[0] * BLOCKSIZE, SEEK_SET);
+
+            pthread_mutex_lock(&nti.mu);
+            nti.rss = &rss;
+            pthread_cond_broadcast(&nti.cv);
+            while (nti.rss) {
+                pthread_cond_wait(&nti.cv, &nti.mu);
+            }
+            pthread_mutex_unlock(&nti.mu);
+
+            blocks_so_far += tgt->size;
+            fprintf(cmd_pipe, "set_progress %.4f\n", (double)blocks_so_far / total_blocks);
+            fflush(cmd_pipe);
+
+            free(tgt);
+
+        } else if (strcmp("bsdiff", style) == 0 ||
+                   strcmp("imgdiff", style) == 0) {
+            word = strtok_r(NULL, " ", &wordsave);
+            size_t patch_offset = strtoul(word, NULL, 0);
+            word = strtok_r(NULL, " ", &wordsave);
+            size_t patch_len = strtoul(word, NULL, 0);
+
+            word = strtok_r(NULL, " ", &wordsave);
+            RangeSet* src = parse_range(word);
+            word = strtok_r(NULL, " ", &wordsave);
+            RangeSet* tgt = parse_range(word);
+
+            printf("  patching %d blocks to %d\n", src->size, tgt->size);
+
+            // Read the source into memory.
+            allocate(src->size * BLOCKSIZE, &buffer, &buffer_alloc);
+            size_t p = 0;
+            for (i = 0; i < src->count; ++i) {
+                check_lseek(fd, src->pos[i*2] * BLOCKSIZE, SEEK_SET);
+                size_t sz = (src->pos[i*2+1] - src->pos[i*2]) * BLOCKSIZE;
+                readblock(fd, buffer+p, sz);
+                p += sz;
+            }
+
+            Value patch_value;
+            patch_value.type = VAL_BLOB;
+            patch_value.size = patch_len;
+            patch_value.data = (char*)(patch_start + patch_offset);
+
+            RangeSinkState rss;
+            rss.fd = fd;
+            rss.tgt = tgt;
+            rss.p_block = 0;
+            rss.p_remain = (tgt->pos[1] - tgt->pos[0]) * BLOCKSIZE;
+            check_lseek(fd, tgt->pos[0] * BLOCKSIZE, SEEK_SET);
+
+            if (style[0] == 'i') {      // imgdiff
+                ApplyImagePatch(buffer, src->size * BLOCKSIZE,
+                                &patch_value,
+                                &RangeSinkWrite, &rss, NULL, NULL);
+            } else {
+                ApplyBSDiffPatch(buffer, src->size * 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");
+            }
+
+            blocks_so_far += tgt->size;
+            fprintf(cmd_pipe, "set_progress %.4f\n", (double)blocks_so_far / total_blocks);
+            fflush(cmd_pipe);
+
+            free(src);
+            free(tgt);
+        } else if (!DEBUG_ERASE && strcmp("erase", style) == 0) {
+            struct stat st;
+            if (fstat(fd, &st) == 0 && S_ISBLK(st.st_mode)) {
+                word = strtok_r(NULL, " ", &wordsave);
+                RangeSet* tgt = parse_range(word);
+
+                printf("  erasing %d blocks\n", tgt->size);
+
+                for (i = 0; i < tgt->count; ++i) {
+                    uint64_t range[2];
+                    // offset in bytes
+                    range[0] = tgt->pos[i*2] * BLOCKSIZE;
+                    // len in bytes
+                    range[1] = (tgt->pos[i*2+1] - tgt->pos[i*2]) * BLOCKSIZE;
+
+                    if (ioctl(fd, BLKDISCARD, &range) < 0) {
+                        printf("    blkdiscard failed: %s\n", strerror(errno));
+                    }
+                }
+
+                free(tgt);
+            } else {
+                printf("  ignoring erase (not block device)\n");
+            }
+        } else {
+            fprintf(stderr, "unknown transfer style \"%s\"\n", style);
+            exit(1);
+        }
+    }
+
+    pthread_join(new_data_thread, NULL);
+    success = true;
+
+    free(buffer);
+    printf("wrote %d blocks; expected %d\n", blocks_so_far, total_blocks);
+    printf("max alloc needed was %zu\n", buffer_alloc);
+
+  done:
+    FreeValue(blockdev_filename);
+    FreeValue(transfer_list);
+    FreeValue(new_data_fn);
+    FreeValue(patch_data_fn);
+    return StringValue(success ? strdup("t") : strdup(""));
+}
+
+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 = open(blockdev_filename->data, O_RDWR);
+    if (fd < 0) {
+        ErrorAbort(state, "failed to open %s: %s", blockdev_filename->data, strerror(errno));
+        goto done;
+    }
+
+    RangeSet* 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) {
+        check_lseek(fd, rs->pos[i*2] * BLOCKSIZE, SEEK_SET);
+        for (j = rs->pos[i*2]; j < rs->pos[i*2+1]; ++j) {
+            readblock(fd, buffer, BLOCKSIZE);
+            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_update", BlockImageUpdateFn);
+    RegisterFunction("range_sha1", RangeSha1Fn);
+}
diff --git a/updater/blockimg.h b/updater/blockimg.h
new file mode 100644
index 0000000..2f4ad3c
--- /dev/null
+++ b/updater/blockimg.h
@@ -0,0 +1,22 @@
+/*
+ * 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.
+ */
+
+#ifndef _UPDATER_BLOCKIMG_H_
+#define _UPDATER_BLOCKIMG_H_
+
+void RegisterBlockImageFunctions();
+
+#endif
diff --git a/updater/install.c b/updater/install.c
index 1986180..cdcdb8f 100644
--- a/updater/install.c
+++ b/updater/install.c
@@ -54,7 +54,7 @@
 #endif
 
 // Take a sha-1 digest and return it as a newly-allocated hex string.
-static char* PrintSha1(const uint8_t* digest) {
+char* PrintSha1(const uint8_t* digest) {
     char* buffer = malloc(SHA_DIGEST_SIZE*2 + 1);
     int i;
     const char* alphabet = "0123456789abcdef";
diff --git a/updater/updater.c b/updater/updater.c
index b7af3e5..465e123 100644
--- a/updater/updater.c
+++ b/updater/updater.c
@@ -21,6 +21,7 @@
 #include "edify/expr.h"
 #include "updater.h"
 #include "install.h"
+#include "blockimg.h"
 #include "minzip/Zip.h"
 #include "minzip/SysUtil.h"
 
@@ -98,6 +99,7 @@
 
     RegisterBuiltins();
     RegisterInstallFunctions();
+    RegisterBlockImageFunctions();
     RegisterDeviceExtensions();
     FinishRegistration();
 
@@ -127,6 +129,8 @@
     updater_info.cmd_pipe = cmd_pipe;
     updater_info.package_zip = &za;
     updater_info.version = atoi(version);
+    updater_info.package_zip_addr = map.addr;
+    updater_info.package_zip_len = map.length;
 
     State state;
     state.cookie = &updater_info;
diff --git a/updater/updater.h b/updater/updater.h
index d2e9011..d1dfdd0 100644
--- a/updater/updater.h
+++ b/updater/updater.h
@@ -27,6 +27,9 @@
     FILE* cmd_pipe;
     ZipArchive* package_zip;
     int version;
+
+    uint8_t* package_zip_addr;
+    size_t package_zip_len;
 } UpdaterInfo;
 
 extern struct selabel_handle *sehandle;