diff --git a/applypatch/imgpatch.cpp b/applypatch/imgpatch.cpp
new file mode 100644
index 0000000..26888f8
--- /dev/null
+++ b/applypatch/imgpatch.cpp
@@ -0,0 +1,234 @@
+/*
+ * Copyright (C) 2009 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.
+ */
+
+// See imgdiff.c in this directory for a description of the patch file
+// format.
+
+#include <stdio.h>
+#include <sys/cdefs.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <malloc.h>
+#include <unistd.h>
+#include <string.h>
+
+#include "zlib.h"
+#include "mincrypt/sha.h"
+#include "applypatch.h"
+#include "imgdiff.h"
+#include "utils.h"
+
+/*
+ * Apply the patch given in 'patch_filename' to the source data given
+ * by (old_data, old_size).  Write the patched output to the 'output'
+ * file, and update the SHA context with the output data as well.
+ * Return 0 on success.
+ */
+int ApplyImagePatch(const unsigned char* old_data, ssize_t old_size __unused,
+                    const Value* patch,
+                    SinkFn sink, void* token, SHA_CTX* ctx,
+                    const Value* bonus_data) {
+    ssize_t pos = 12;
+    char* header = patch->data;
+    if (patch->size < 12) {
+        printf("patch too short to contain header\n");
+        return -1;
+    }
+
+    // IMGDIFF2 uses CHUNK_NORMAL, CHUNK_DEFLATE, and CHUNK_RAW.
+    // (IMGDIFF1, which is no longer supported, used CHUNK_NORMAL and
+    // CHUNK_GZIP.)
+    if (memcmp(header, "IMGDIFF2", 8) != 0) {
+        printf("corrupt patch file header (magic number)\n");
+        return -1;
+    }
+
+    int num_chunks = Read4(header+8);
+
+    int i;
+    for (i = 0; i < num_chunks; ++i) {
+        // each chunk's header record starts with 4 bytes.
+        if (pos + 4 > patch->size) {
+            printf("failed to read chunk %d record\n", i);
+            return -1;
+        }
+        int type = Read4(patch->data + pos);
+        pos += 4;
+
+        if (type == CHUNK_NORMAL) {
+            char* normal_header = patch->data + pos;
+            pos += 24;
+            if (pos > patch->size) {
+                printf("failed to read chunk %d normal header data\n", i);
+                return -1;
+            }
+
+            size_t src_start = Read8(normal_header);
+            size_t src_len = Read8(normal_header+8);
+            size_t patch_offset = Read8(normal_header+16);
+
+            ApplyBSDiffPatch(old_data + src_start, src_len,
+                             patch, patch_offset, sink, token, ctx);
+        } else if (type == CHUNK_RAW) {
+            char* raw_header = patch->data + pos;
+            pos += 4;
+            if (pos > patch->size) {
+                printf("failed to read chunk %d raw header data\n", i);
+                return -1;
+            }
+
+            ssize_t data_len = Read4(raw_header);
+
+            if (pos + data_len > patch->size) {
+                printf("failed to read chunk %d raw data\n", i);
+                return -1;
+            }
+            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);
+                return -1;
+            }
+            pos += data_len;
+        } else if (type == CHUNK_DEFLATE) {
+            // deflate chunks have an additional 60 bytes in their chunk header.
+            char* deflate_header = patch->data + pos;
+            pos += 60;
+            if (pos > patch->size) {
+                printf("failed to read chunk %d deflate header data\n", i);
+                return -1;
+            }
+
+            size_t src_start = Read8(deflate_header);
+            size_t src_len = Read8(deflate_header+8);
+            size_t patch_offset = Read8(deflate_header+16);
+            size_t expanded_len = Read8(deflate_header+24);
+            size_t target_len = Read8(deflate_header+32);
+            int level = Read4(deflate_header+40);
+            int method = Read4(deflate_header+44);
+            int windowBits = Read4(deflate_header+48);
+            int memLevel = Read4(deflate_header+52);
+            int strategy = Read4(deflate_header+56);
+
+            // Decompress the source data; the chunk header tells us exactly
+            // how big we expect it to be when decompressed.
+
+            // Note: expanded_len will include the bonus data size if
+            // the patch was constructed with bonus data.  The
+            // deflation will come up 'bonus_size' bytes short; these
+            // must be appended from the bonus_data value.
+            size_t bonus_size = (i == 1 && bonus_data != NULL) ? bonus_data->size : 0;
+
+            unsigned char* expanded_source = reinterpret_cast<unsigned char*>(malloc(expanded_len));
+            if (expanded_source == NULL) {
+                printf("failed to allocate %zu bytes for expanded_source\n",
+                       expanded_len);
+                return -1;
+            }
+
+            z_stream strm;
+            strm.zalloc = Z_NULL;
+            strm.zfree = Z_NULL;
+            strm.opaque = Z_NULL;
+            strm.avail_in = src_len;
+            strm.next_in = (unsigned char*)(old_data + src_start);
+            strm.avail_out = expanded_len;
+            strm.next_out = expanded_source;
+
+            int ret;
+            ret = inflateInit2(&strm, -15);
+            if (ret != Z_OK) {
+                printf("failed to init source inflation: %d\n", ret);
+                return -1;
+            }
+
+            // Because we've provided enough room to accommodate the output
+            // data, we expect one call to inflate() to suffice.
+            ret = inflate(&strm, Z_SYNC_FLUSH);
+            if (ret != Z_STREAM_END) {
+                printf("source inflation returned %d\n", ret);
+                return -1;
+            }
+            // We should have filled the output buffer exactly, except
+            // for the bonus_size.
+            if (strm.avail_out != bonus_size) {
+                printf("source inflation short by %zu bytes\n", strm.avail_out-bonus_size);
+                return -1;
+            }
+            inflateEnd(&strm);
+
+            if (bonus_size) {
+                memcpy(expanded_source + (expanded_len - bonus_size),
+                       bonus_data->data, bonus_size);
+            }
+
+            // Next, apply the bsdiff patch (in memory) to the uncompressed
+            // data.
+            unsigned char* uncompressed_target_data;
+            ssize_t uncompressed_target_size;
+            if (ApplyBSDiffPatchMem(expanded_source, expanded_len,
+                                    patch, patch_offset,
+                                    &uncompressed_target_data,
+                                    &uncompressed_target_size) != 0) {
+                return -1;
+            }
+
+            // Now compress the target data and append it to the output.
+
+            // we're done with the expanded_source data buffer, so we'll
+            // reuse that memory to receive the output of deflate.
+            unsigned char* temp_data = expanded_source;
+            ssize_t temp_size = expanded_len;
+            if (temp_size < 32768) {
+                // ... unless the buffer is too small, in which case we'll
+                // allocate a fresh one.
+                free(temp_data);
+                temp_data = reinterpret_cast<unsigned char*>(malloc(32768));
+                temp_size = 32768;
+            }
+
+            // now the deflate stream
+            strm.zalloc = Z_NULL;
+            strm.zfree = Z_NULL;
+            strm.opaque = Z_NULL;
+            strm.avail_in = uncompressed_target_size;
+            strm.next_in = uncompressed_target_data;
+            ret = deflateInit2(&strm, level, method, windowBits, memLevel, strategy);
+            do {
+                strm.avail_out = temp_size;
+                strm.next_out = temp_data;
+                ret = deflate(&strm, Z_FINISH);
+                ssize_t have = temp_size - strm.avail_out;
+
+                if (sink(temp_data, have, token) != have) {
+                    printf("failed to write %ld compressed bytes to output\n",
+                           (long)have);
+                    return -1;
+                }
+                if (ctx) SHA_update(ctx, temp_data, have);
+            } while (ret != Z_STREAM_END);
+            deflateEnd(&strm);
+
+            free(temp_data);
+            free(uncompressed_target_data);
+        } else {
+            printf("patch chunk %d is unknown type %d\n", i, type);
+            return -1;
+        }
+    }
+
+    return 0;
+}