diff --git a/applypatch/bspatch.c b/applypatch/bspatch.c
new file mode 100644
index 0000000..2e80f81
--- /dev/null
+++ b/applypatch/bspatch.c
@@ -0,0 +1,252 @@
+/*
+ * Copyright (C) 2008 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.
+ */
+
+// This file is a nearly line-for-line copy of bspatch.c from the
+// bsdiff-4.3 distribution; the primary differences being how the
+// input and output data are read and the error handling.  Running
+// applypatch with the -l option will display the bsdiff license
+// notice.
+
+#include <stdio.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <unistd.h>
+#include <string.h>
+
+#include <bzlib.h>
+
+#include "mincrypt/sha.h"
+#include "applypatch.h"
+
+void ShowBSDiffLicense() {
+    puts("The bsdiff library used herein is:\n"
+         "\n"
+         "Copyright 2003-2005 Colin Percival\n"
+         "All rights reserved\n"
+         "\n"
+         "Redistribution and use in source and binary forms, with or without\n"
+         "modification, are permitted providing that the following conditions\n"
+         "are met:\n"
+         "1. Redistributions of source code must retain the above copyright\n"
+         "   notice, this list of conditions and the following disclaimer.\n"
+         "2. Redistributions in binary form must reproduce the above copyright\n"
+         "   notice, this list of conditions and the following disclaimer in the\n"
+         "   documentation and/or other materials provided with the distribution.\n"
+         "\n"
+         "THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR\n"
+         "IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED\n"
+         "WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE\n"
+         "ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY\n"
+         "DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL\n"
+         "DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS\n"
+         "OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)\n"
+         "HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,\n"
+         "STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING\n"
+         "IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE\n"
+         "POSSIBILITY OF SUCH DAMAGE.\n"
+         "\n------------------\n\n"
+         "This program uses Julian R Seward's \"libbzip2\" library, available\n"
+         "from http://www.bzip.org/.\n"
+        );
+}
+
+static off_t offtin(u_char *buf)
+{
+    off_t y;
+
+    y=buf[7]&0x7F;
+    y=y*256;y+=buf[6];
+    y=y*256;y+=buf[5];
+    y=y*256;y+=buf[4];
+    y=y*256;y+=buf[3];
+    y=y*256;y+=buf[2];
+    y=y*256;y+=buf[1];
+    y=y*256;y+=buf[0];
+
+    if(buf[7]&0x80) y=-y;
+
+    return y;
+}
+
+int FillBuffer(unsigned char* buffer, int size, bz_stream* stream) {
+    stream->next_out = (char*)buffer;
+    stream->avail_out = size;
+    while (stream->avail_out > 0) {
+        int bzerr = BZ2_bzDecompress(stream);
+        if (bzerr != BZ_OK && bzerr != BZ_STREAM_END) {
+            printf("bz error %d decompressing\n", bzerr);
+            return -1;
+        }
+        if (stream->avail_out > 0) {
+            printf("need %d more bytes\n", stream->avail_out);
+        }
+    }
+    return 0;
+}
+
+int ApplyBSDiffPatch(const unsigned char* old_data, ssize_t old_size,
+                     const Value* patch, ssize_t patch_offset,
+                     SinkFn sink, void* token, SHA_CTX* ctx) {
+
+    unsigned char* new_data;
+    ssize_t new_size;
+    if (ApplyBSDiffPatchMem(old_data, old_size, patch, patch_offset,
+                            &new_data, &new_size) != 0) {
+        return -1;
+    }
+
+    if (sink(new_data, new_size, token) < new_size) {
+        printf("short write of output: %d (%s)\n", errno, strerror(errno));
+        return 1;
+    }
+    if (ctx) {
+        SHA_update(ctx, new_data, new_size);
+    }
+    free(new_data);
+
+    return 0;
+}
+
+int ApplyBSDiffPatchMem(const unsigned char* old_data, ssize_t old_size,
+                        const Value* patch, ssize_t patch_offset,
+                        unsigned char** new_data, ssize_t* new_size) {
+    // Patch data format:
+    //   0       8       "BSDIFF40"
+    //   8       8       X
+    //   16      8       Y
+    //   24      8       sizeof(newfile)
+    //   32      X       bzip2(control block)
+    //   32+X    Y       bzip2(diff block)
+    //   32+X+Y  ???     bzip2(extra block)
+    // with control block a set of triples (x,y,z) meaning "add x bytes
+    // from oldfile to x bytes from the diff block; copy y bytes from the
+    // extra block; seek forwards in oldfile by z bytes".
+
+    unsigned char* header = (unsigned char*) patch->data + patch_offset;
+    if (memcmp(header, "BSDIFF40", 8) != 0) {
+        printf("corrupt bsdiff patch file header (magic number)\n");
+        return 1;
+    }
+
+    ssize_t ctrl_len, data_len;
+    ctrl_len = offtin(header+8);
+    data_len = offtin(header+16);
+    *new_size = offtin(header+24);
+
+    if (ctrl_len < 0 || data_len < 0 || *new_size < 0) {
+        printf("corrupt patch file header (data lengths)\n");
+        return 1;
+    }
+
+    int bzerr;
+
+    bz_stream cstream;
+    cstream.next_in = patch->data + patch_offset + 32;
+    cstream.avail_in = ctrl_len;
+    cstream.bzalloc = NULL;
+    cstream.bzfree = NULL;
+    cstream.opaque = NULL;
+    if ((bzerr = BZ2_bzDecompressInit(&cstream, 0, 0)) != BZ_OK) {
+        printf("failed to bzinit control stream (%d)\n", bzerr);
+    }
+
+    bz_stream dstream;
+    dstream.next_in = patch->data + patch_offset + 32 + ctrl_len;
+    dstream.avail_in = data_len;
+    dstream.bzalloc = NULL;
+    dstream.bzfree = NULL;
+    dstream.opaque = NULL;
+    if ((bzerr = BZ2_bzDecompressInit(&dstream, 0, 0)) != BZ_OK) {
+        printf("failed to bzinit diff stream (%d)\n", bzerr);
+    }
+
+    bz_stream estream;
+    estream.next_in = patch->data + patch_offset + 32 + ctrl_len + data_len;
+    estream.avail_in = patch->size - (patch_offset + 32 + ctrl_len + data_len);
+    estream.bzalloc = NULL;
+    estream.bzfree = NULL;
+    estream.opaque = NULL;
+    if ((bzerr = BZ2_bzDecompressInit(&estream, 0, 0)) != BZ_OK) {
+        printf("failed to bzinit extra stream (%d)\n", bzerr);
+    }
+
+    *new_data = malloc(*new_size);
+    if (*new_data == NULL) {
+        printf("failed to allocate %ld bytes of memory for output file\n",
+               (long)*new_size);
+        return 1;
+    }
+
+    off_t oldpos = 0, newpos = 0;
+    off_t ctrl[3];
+    off_t len_read;
+    int i;
+    unsigned char buf[24];
+    while (newpos < *new_size) {
+        // Read control data
+        if (FillBuffer(buf, 24, &cstream) != 0) {
+            printf("error while reading control stream\n");
+            return 1;
+        }
+        ctrl[0] = offtin(buf);
+        ctrl[1] = offtin(buf+8);
+        ctrl[2] = offtin(buf+16);
+
+        // Sanity check
+        if (newpos + ctrl[0] > *new_size) {
+            printf("corrupt patch (new file overrun)\n");
+            return 1;
+        }
+
+        // Read diff string
+        if (FillBuffer(*new_data + newpos, ctrl[0], &dstream) != 0) {
+            printf("error while reading diff stream\n");
+            return 1;
+        }
+
+        // Add old data to diff string
+        for (i = 0; i < ctrl[0]; ++i) {
+            if ((oldpos+i >= 0) && (oldpos+i < old_size)) {
+                (*new_data)[newpos+i] += old_data[oldpos+i];
+            }
+        }
+
+        // Adjust pointers
+        newpos += ctrl[0];
+        oldpos += ctrl[0];
+
+        // Sanity check
+        if (newpos + ctrl[1] > *new_size) {
+            printf("corrupt patch (new file overrun)\n");
+            return 1;
+        }
+
+        // Read extra string
+        if (FillBuffer(*new_data + newpos, ctrl[1], &estream) != 0) {
+            printf("error while reading extra stream\n");
+            return 1;
+        }
+
+        // Adjust pointers
+        newpos += ctrl[1];
+        oldpos += ctrl[2];
+    }
+
+    BZ2_bzDecompressEnd(&cstream);
+    BZ2_bzDecompressEnd(&dstream);
+    BZ2_bzDecompressEnd(&estream);
+    return 0;
+}