diff --git a/applypatch/applypatch.cpp b/applypatch/applypatch.cpp
index 06b8e31..51bf393 100644
--- a/applypatch/applypatch.cpp
+++ b/applypatch/applypatch.cpp
@@ -27,6 +27,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include <functional>
 #include <memory>
 #include <string>
 #include <utility>
@@ -42,7 +43,7 @@
 #include "print_sha1.h"
 
 static int LoadPartitionContents(const std::string& filename, FileContents* file);
-static size_t FileSink(const unsigned char* data, size_t len, void* token);
+static size_t FileSink(const unsigned char* data, size_t len, int fd);
 static int GenerateTarget(const FileContents& source_file, const std::unique_ptr<Value>& patch,
                           const std::string& target_filename,
                           const uint8_t target_sha1[SHA_DIGEST_LENGTH], const Value* bonus_data);
@@ -194,7 +195,7 @@
     return -1;
   }
 
-  size_t bytes_written = FileSink(file->data.data(), file->data.size(), &fd);
+  size_t bytes_written = FileSink(file->data.data(), file->data.size(), fd);
   if (bytes_written != file->data.size()) {
     printf("short write of \"%s\" (%zd bytes of %zu): %s\n", filename, bytes_written,
            file->data.size(), strerror(errno));
@@ -433,8 +434,7 @@
     return 0;
 }
 
-static size_t FileSink(const unsigned char* data, size_t len, void* token) {
-  int fd = *static_cast<int*>(token);
+static size_t FileSink(const unsigned char* data, size_t len, int fd) {
   size_t done = 0;
   while (done < len) {
     ssize_t wrote = TEMP_FAILURE_RETRY(ota_write(fd, data + done, len - done));
@@ -447,12 +447,6 @@
   return done;
 }
 
-size_t MemorySink(const unsigned char* data, size_t len, void* token) {
-  std::string* s = static_cast<std::string*>(token);
-  s->append(reinterpret_cast<const char*>(data), len);
-  return len;
-}
-
 // Return the amount of free space (in bytes) on the filesystem
 // containing filename.  filename must exist.  Return -1 on error.
 size_t FreeSpaceForFile(const char* filename) {
@@ -646,9 +640,11 @@
   }
 
   // We store the decoded output in memory.
-  SinkFn sink = MemorySink;
   std::string memory_sink_str;  // Don't need to reserve space.
-  void* token = &memory_sink_str;
+  SinkFn sink = [&memory_sink_str](const unsigned char* data, size_t len) {
+    memory_sink_str.append(reinterpret_cast<const char*>(data), len);
+    return len;
+  };
 
   SHA_CTX ctx;
   SHA1_Init(&ctx);
@@ -656,10 +652,10 @@
   int result;
   if (use_bsdiff) {
     result = ApplyBSDiffPatch(source_file.data.data(), source_file.data.size(), patch.get(), 0,
-                              sink, token, &ctx);
+                              sink, &ctx);
   } else {
     result = ApplyImagePatch(source_file.data.data(), source_file.data.size(), patch.get(), sink,
-                             token, &ctx, bonus_data);
+                             &ctx, bonus_data);
   }
 
   if (result != 0) {
diff --git a/applypatch/bspatch.cpp b/applypatch/bspatch.cpp
index 8ef7a06..f75a2c6 100644
--- a/applypatch/bspatch.cpp
+++ b/applypatch/bspatch.cpp
@@ -24,9 +24,9 @@
 #include <sys/types.h>
 
 #include <bspatch.h>
+#include <openssl/sha.h>
 
 #include "applypatch/applypatch.h"
-#include "openssl/sha.h"
 
 void ShowBSDiffLicense() {
     puts("The bsdiff library used herein is:\n"
@@ -61,9 +61,9 @@
 }
 
 int ApplyBSDiffPatch(const unsigned char* old_data, size_t old_size, const Value* patch,
-                     size_t patch_offset, SinkFn sink, void* token, SHA_CTX* ctx) {
-  auto sha_sink = [&](const uint8_t* data, size_t len) {
-    len = sink(data, len, token);
+                     size_t patch_offset, SinkFn sink, SHA_CTX* ctx) {
+  auto sha_sink = [&sink, &ctx](const uint8_t* data, size_t len) {
+    len = sink(data, len);
     if (ctx) SHA1_Update(ctx, data, len);
     return len;
   };
diff --git a/applypatch/imgpatch.cpp b/applypatch/imgpatch.cpp
index 7a88ffb..7d8b736 100644
--- a/applypatch/imgpatch.cpp
+++ b/applypatch/imgpatch.cpp
@@ -44,10 +44,10 @@
 }
 
 int ApplyImagePatch(const unsigned char* old_data, size_t old_size, const unsigned char* patch_data,
-                    size_t patch_size, SinkFn sink, void* token) {
+                    size_t patch_size, SinkFn sink) {
   Value patch(VAL_BLOB, std::string(reinterpret_cast<const char*>(patch_data), patch_size));
 
-  return ApplyImagePatch(old_data, old_size, &patch, sink, token, nullptr, nullptr);
+  return ApplyImagePatch(old_data, old_size, &patch, sink, nullptr, nullptr);
 }
 
 /*
@@ -57,7 +57,7 @@
  * Return 0 on success.
  */
 int ApplyImagePatch(const unsigned char* old_data, size_t old_size, const Value* patch, SinkFn sink,
-                    void* token, SHA_CTX* ctx, const Value* bonus_data) {
+                    SHA_CTX* ctx, const Value* bonus_data) {
   if (patch->data.size() < 12) {
     printf("patch too short to contain header\n");
     return -1;
@@ -100,7 +100,7 @@
         printf("source data too short\n");
         return -1;
       }
-      ApplyBSDiffPatch(old_data + src_start, src_len, patch, patch_offset, sink, token, ctx);
+      ApplyBSDiffPatch(old_data + src_start, src_len, patch, patch_offset, sink, ctx);
     } else if (type == CHUNK_RAW) {
       const char* raw_header = &patch->data[pos];
       pos += 4;
@@ -116,8 +116,7 @@
         return -1;
       }
       if (ctx) SHA1_Update(ctx, &patch->data[pos], data_len);
-      if (sink(reinterpret_cast<const unsigned char*>(&patch->data[pos]), data_len, token) !=
-          data_len) {
+      if (sink(reinterpret_cast<const unsigned char*>(&patch->data[pos]), data_len) != data_len) {
         printf("failed to write chunk %d raw data\n", i);
         return -1;
       }
@@ -241,7 +240,7 @@
           ret = deflate(&strm, Z_FINISH);
           size_t have = temp_data.size() - strm.avail_out;
 
-          if (sink(temp_data.data(), have, token) != have) {
+          if (sink(temp_data.data(), have) != have) {
             printf("failed to write %zd compressed bytes to output\n", have);
             return -1;
           }
diff --git a/applypatch/include/applypatch/applypatch.h b/applypatch/include/applypatch/applypatch.h
index 52fb582..da55432 100644
--- a/applypatch/include/applypatch/applypatch.h
+++ b/applypatch/include/applypatch/applypatch.h
@@ -20,6 +20,7 @@
 #include <stdint.h>
 #include <sys/stat.h>
 
+#include <functional>
 #include <memory>
 #include <string>
 #include <vector>
@@ -41,7 +42,7 @@
 // and use it as the source instead.
 #define CACHE_TEMP_SOURCE "/cache/saved.file"
 
-using SinkFn = size_t (*)(const unsigned char*, size_t, void*);
+using SinkFn = std::function<size_t(const unsigned char*, size_t)>;
 
 // applypatch.cpp
 int ShowLicenses();
@@ -67,13 +68,13 @@
 // bspatch.cpp
 void ShowBSDiffLicense();
 int ApplyBSDiffPatch(const unsigned char* old_data, size_t old_size, const Value* patch,
-                     size_t patch_offset, SinkFn sink, void* token, SHA_CTX* ctx);
+                     size_t patch_offset, SinkFn sink, SHA_CTX* ctx);
 int ApplyBSDiffPatchMem(const unsigned char* old_data, size_t old_size, const Value* patch,
                         size_t patch_offset, std::vector<unsigned char>* new_data);
 
 // imgpatch.cpp
 int ApplyImagePatch(const unsigned char* old_data, size_t old_size, const Value* patch, SinkFn sink,
-                    void* token, SHA_CTX* ctx, const Value* bonus_data);
+                    SHA_CTX* ctx, const Value* bonus_data);
 
 // freecache.cpp
 int MakeFreeSpaceOnCache(size_t bytes_needed);
diff --git a/applypatch/include/applypatch/imgpatch.h b/applypatch/include/applypatch/imgpatch.h
index 16e4c4f..07c6609 100644
--- a/applypatch/include/applypatch/imgpatch.h
+++ b/applypatch/include/applypatch/imgpatch.h
@@ -19,9 +19,11 @@
 
 #include <sys/types.h>
 
-using SinkFn = size_t (*)(const unsigned char*, size_t, void*);
+#include <functional>
+
+using SinkFn = std::function<size_t(const unsigned char*, size_t)>;
 
 int ApplyImagePatch(const unsigned char* old_data, size_t old_size, const unsigned char* patch_data,
-                    size_t patch_size, SinkFn sink, void* token);
+                    size_t patch_size, SinkFn sink);
 
 #endif  // _APPLYPATCH_IMGPATCH_H
diff --git a/tests/component/imgdiff_test.cpp b/tests/component/imgdiff_test.cpp
index 64e1f29..7d00a3d 100644
--- a/tests/component/imgdiff_test.cpp
+++ b/tests/component/imgdiff_test.cpp
@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+#include <stdio.h>
+
 #include <string>
 #include <vector>
 
@@ -27,12 +29,6 @@
 
 using android::base::get_unaligned;
 
-static size_t MemorySink(const unsigned char* data, size_t len, void* token) {
-  std::string* s = static_cast<std::string*>(token);
-  s->append(reinterpret_cast<const char*>(data), len);
-  return len;
-}
-
 // Sanity check for the given imgdiff patch header.
 static void verify_patch_header(const std::string& patch, size_t* num_normal, size_t* num_raw,
                                 size_t* num_deflate) {
@@ -79,6 +75,18 @@
   if (num_deflate != nullptr) *num_deflate = deflate;
 }
 
+static void verify_patched_image(const std::string& src, const std::string& patch,
+                                 const std::string& tgt) {
+  std::string patched;
+  ASSERT_EQ(0, ApplyImagePatch(reinterpret_cast<const unsigned char*>(src.data()), src.size(),
+                               reinterpret_cast<const unsigned char*>(patch.data()), patch.size(),
+                               [&patched](const unsigned char* data, size_t len) {
+                                 patched.append(reinterpret_cast<const char*>(data), len);
+                                 return len;
+                               }));
+  ASSERT_EQ(tgt, patched);
+}
+
 TEST(ImgdiffTest, invalid_args) {
   // Insufficient inputs.
   ASSERT_EQ(2, imgdiff(1, (const char* []){ "imgdiff" }));
@@ -124,11 +132,7 @@
   ASSERT_EQ(0U, num_deflate);
   ASSERT_EQ(1U, num_raw);
 
-  std::string patched;
-  ASSERT_EQ(0, ApplyImagePatch(reinterpret_cast<const unsigned char*>(src.data()), src.size(),
-                               reinterpret_cast<const unsigned char*>(patch.data()), patch.size(),
-                               MemorySink, &patched));
-  ASSERT_EQ(tgt, patched);
+  verify_patched_image(src, patch, tgt);
 }
 
 TEST(ImgdiffTest, zip_mode_smoke_store) {
@@ -177,11 +181,7 @@
   ASSERT_EQ(0U, num_deflate);
   ASSERT_EQ(1U, num_raw);
 
-  std::string patched;
-  ASSERT_EQ(0, ApplyImagePatch(reinterpret_cast<const unsigned char*>(src.data()), src.size(),
-                               reinterpret_cast<const unsigned char*>(patch.data()), patch.size(),
-                               MemorySink, &patched));
-  ASSERT_EQ(tgt, patched);
+  verify_patched_image(src, patch, tgt);
 }
 
 TEST(ImgdiffTest, zip_mode_smoke_compressed) {
@@ -230,11 +230,7 @@
   ASSERT_EQ(1U, num_deflate);
   ASSERT_EQ(2U, num_raw);
 
-  std::string patched;
-  ASSERT_EQ(0, ApplyImagePatch(reinterpret_cast<const unsigned char*>(src.data()), src.size(),
-                               reinterpret_cast<const unsigned char*>(patch.data()), patch.size(),
-                               MemorySink, &patched));
-  ASSERT_EQ(tgt, patched);
+  verify_patched_image(src, patch, tgt);
 }
 
 TEST(ImgdiffTest, zip_mode_smoke_trailer_zeros) {
@@ -286,11 +282,7 @@
   ASSERT_EQ(1U, num_deflate);
   ASSERT_EQ(2U, num_raw);
 
-  std::string patched;
-  ASSERT_EQ(0, ApplyImagePatch(reinterpret_cast<const unsigned char*>(src.data()), src.size(),
-                               reinterpret_cast<const unsigned char*>(patch.data()), patch.size(),
-                               MemorySink, &patched));
-  ASSERT_EQ(tgt, patched);
+  verify_patched_image(src, patch, tgt);
 }
 
 TEST(ImgdiffTest, image_mode_simple) {
@@ -333,11 +325,7 @@
   ASSERT_EQ(1U, num_deflate);
   ASSERT_EQ(2U, num_raw);
 
-  std::string patched;
-  ASSERT_EQ(0, ApplyImagePatch(reinterpret_cast<const unsigned char*>(src.data()), src.size(),
-                               reinterpret_cast<const unsigned char*>(patch.data()), patch.size(),
-                               MemorySink, &patched));
-  ASSERT_EQ(tgt, patched);
+  verify_patched_image(src, patch, tgt);
 }
 
 TEST(ImgdiffTest, image_mode_different_num_chunks) {
@@ -413,11 +401,7 @@
   ASSERT_EQ(1U, num_deflate);
   ASSERT_EQ(2U, num_raw);
 
-  std::string patched;
-  ASSERT_EQ(0, ApplyImagePatch(reinterpret_cast<const unsigned char*>(src.data()), src.size(),
-                               reinterpret_cast<const unsigned char*>(patch.data()), patch.size(),
-                               MemorySink, &patched));
-  ASSERT_EQ(tgt, patched);
+  verify_patched_image(src, patch, tgt);
 }
 
 TEST(ImgdiffTest, image_mode_spurious_magic) {
@@ -454,11 +438,7 @@
   ASSERT_EQ(0U, num_deflate);
   ASSERT_EQ(1U, num_raw);
 
-  std::string patched;
-  ASSERT_EQ(0, ApplyImagePatch(reinterpret_cast<const unsigned char*>(src.data()), src.size(),
-                               reinterpret_cast<const unsigned char*>(patch.data()), patch.size(),
-                               MemorySink, &patched));
-  ASSERT_EQ(tgt, patched);
+  verify_patched_image(src, patch, tgt);
 }
 
 TEST(ImgdiffTest, image_mode_short_input1) {
@@ -494,11 +474,7 @@
   ASSERT_EQ(0U, num_deflate);
   ASSERT_EQ(1U, num_raw);
 
-  std::string patched;
-  ASSERT_EQ(0, ApplyImagePatch(reinterpret_cast<const unsigned char*>(src.data()), src.size(),
-                               reinterpret_cast<const unsigned char*>(patch.data()), patch.size(),
-                               MemorySink, &patched));
-  ASSERT_EQ(tgt, patched);
+  verify_patched_image(src, patch, tgt);
 }
 
 TEST(ImgdiffTest, image_mode_short_input2) {
@@ -534,11 +510,7 @@
   ASSERT_EQ(0U, num_deflate);
   ASSERT_EQ(1U, num_raw);
 
-  std::string patched;
-  ASSERT_EQ(0, ApplyImagePatch(reinterpret_cast<const unsigned char*>(src.data()), src.size(),
-                               reinterpret_cast<const unsigned char*>(patch.data()), patch.size(),
-                               MemorySink, &patched));
-  ASSERT_EQ(tgt, patched);
+  verify_patched_image(src, patch, tgt);
 }
 
 TEST(ImgdiffTest, image_mode_single_entry_long) {
@@ -577,9 +549,5 @@
   ASSERT_EQ(0U, num_deflate);
   ASSERT_EQ(0U, num_raw);
 
-  std::string patched;
-  ASSERT_EQ(0, ApplyImagePatch(reinterpret_cast<const unsigned char*>(src.data()), src.size(),
-                               reinterpret_cast<const unsigned char*>(patch.data()), patch.size(),
-                               MemorySink, &patched));
-  ASSERT_EQ(tgt, patched);
+  verify_patched_image(src, patch, tgt);
 }
diff --git a/updater/blockimg.cpp b/updater/blockimg.cpp
index 5a27ff4..8c0f885 100644
--- a/updater/blockimg.cpp
+++ b/updater/blockimg.cpp
@@ -240,9 +240,7 @@
     size_t p_remain;
 };
 
-static size_t RangeSinkWrite(const uint8_t* data, size_t size, void* token) {
-  RangeSinkState* rss = static_cast<RangeSinkState*>(token);
-
+static size_t RangeSinkWrite(const uint8_t* data, size_t size, RangeSinkState* rss) {
   if (rss->p_remain == 0) {
     LOG(ERROR) << "range sink write overrun";
     return 0;
@@ -1258,92 +1256,95 @@
 }
 
 static int PerformCommandDiff(CommandParameters& params) {
+  // <offset> <length>
+  if (params.cpos + 1 >= params.tokens.size()) {
+    LOG(ERROR) << "missing patch offset or length for " << params.cmdname;
+    return -1;
+  }
 
-    // <offset> <length>
-    if (params.cpos + 1 >= params.tokens.size()) {
-        LOG(ERROR) << "missing patch offset or length for " << params.cmdname;
-        return -1;
-    }
+  size_t offset;
+  if (!android::base::ParseUint(params.tokens[params.cpos++], &offset)) {
+    LOG(ERROR) << "invalid patch offset";
+    return -1;
+  }
 
-    size_t offset;
-    if (!android::base::ParseUint(params.tokens[params.cpos++], &offset)) {
-        LOG(ERROR) << "invalid patch offset";
-        return -1;
-    }
+  size_t len;
+  if (!android::base::ParseUint(params.tokens[params.cpos++], &len)) {
+    LOG(ERROR) << "invalid patch len";
+    return -1;
+  }
 
-    size_t len;
-    if (!android::base::ParseUint(params.tokens[params.cpos++], &len)) {
-        LOG(ERROR) << "invalid patch len";
-        return -1;
-    }
+  RangeSet tgt;
+  size_t blocks = 0;
+  bool overlap = false;
+  int status = LoadSrcTgtVersion3(params, tgt, &blocks, false, &overlap);
 
-    RangeSet tgt;
-    size_t blocks = 0;
-    bool overlap = false;
-    int status = LoadSrcTgtVersion3(params, tgt, &blocks, false, &overlap);
+  if (status == -1) {
+    LOG(ERROR) << "failed to read blocks for diff";
+    return -1;
+  }
 
-    if (status == -1) {
-        LOG(ERROR) << "failed to read blocks for diff";
-        return -1;
-    }
+  if (status == 0) {
+    params.foundwrites = true;
+  } else if (params.foundwrites) {
+    LOG(WARNING) << "warning: commands executed out of order [" << params.cmdname << "]";
+  }
 
+  if (params.canwrite) {
     if (status == 0) {
-        params.foundwrites = true;
-    } else if (params.foundwrites) {
-        LOG(WARNING) << "warning: commands executed out of order [" << params.cmdname << "]";
-    }
+      LOG(INFO) << "patching " << blocks << " blocks to " << tgt.size;
+      Value patch_value(
+          VAL_BLOB, std::string(reinterpret_cast<const char*>(params.patch_start + offset), len));
+      RangeSinkState rss(tgt);
+      rss.fd = params.fd;
+      rss.p_block = 0;
+      rss.p_remain = (tgt.pos[1] - tgt.pos[0]) * BLOCKSIZE;
 
-    if (params.canwrite) {
-        if (status == 0) {
-            LOG(INFO) << "patching " << blocks << " blocks to " << tgt.size;
-            Value patch_value(VAL_BLOB,
-                    std::string(reinterpret_cast<const char*>(params.patch_start + offset), len));
-            RangeSinkState rss(tgt);
-            rss.fd = params.fd;
-            rss.p_block = 0;
-            rss.p_remain = (tgt.pos[1] - tgt.pos[0]) * BLOCKSIZE;
+      off64_t offset = static_cast<off64_t>(tgt.pos[0]) * BLOCKSIZE;
+      if (!discard_blocks(params.fd, offset, rss.p_remain)) {
+        return -1;
+      }
 
-            off64_t offset = static_cast<off64_t>(tgt.pos[0]) * BLOCKSIZE;
-            if (!discard_blocks(params.fd, offset, rss.p_remain)) {
-                return -1;
-            }
+      if (!check_lseek(params.fd, offset, SEEK_SET)) {
+        return -1;
+      }
 
-            if (!check_lseek(params.fd, offset, SEEK_SET)) {
-                return -1;
-            }
-
-            if (params.cmdname[0] == 'i') {      // imgdiff
-                if (ApplyImagePatch(params.buffer.data(), blocks * BLOCKSIZE, &patch_value,
-                        &RangeSinkWrite, &rss, nullptr, nullptr) != 0) {
-                    LOG(ERROR) << "Failed to apply image patch.";
-                    return -1;
-                }
-            } else {
-                if (ApplyBSDiffPatch(params.buffer.data(), blocks * BLOCKSIZE, &patch_value,
-                        0, &RangeSinkWrite, &rss, nullptr) != 0) {
-                    LOG(ERROR) << "Failed to apply bsdiff patch.";
-                    return -1;
-                }
-            }
-
-            // We expect the output of the patcher to fill the tgt ranges exactly.
-            if (rss.p_block != tgt.count || rss.p_remain != 0) {
-                LOG(ERROR) << "range sink underrun?";
-            }
-        } else {
-            LOG(INFO) << "skipping " << blocks << " blocks already patched to " << tgt.size
-                      << " [" << params.cmdline << "]";
+      if (params.cmdname[0] == 'i') {  // imgdiff
+        if (ApplyImagePatch(
+                params.buffer.data(), blocks * BLOCKSIZE, &patch_value,
+                std::bind(&RangeSinkWrite, std::placeholders::_1, std::placeholders::_2, &rss),
+                nullptr, nullptr) != 0) {
+          LOG(ERROR) << "Failed to apply image patch.";
+          return -1;
         }
+      } else {
+        if (ApplyBSDiffPatch(
+                params.buffer.data(), blocks * BLOCKSIZE, &patch_value, 0,
+                std::bind(&RangeSinkWrite, std::placeholders::_1, std::placeholders::_2, &rss),
+                nullptr) != 0) {
+          LOG(ERROR) << "Failed to apply bsdiff patch.";
+          return -1;
+        }
+      }
+
+      // We expect the output of the patcher to fill the tgt ranges exactly.
+      if (rss.p_block != tgt.count || rss.p_remain != 0) {
+        LOG(ERROR) << "range sink underrun?";
+      }
+    } else {
+      LOG(INFO) << "skipping " << blocks << " blocks already patched to " << tgt.size << " ["
+                << params.cmdline << "]";
     }
+  }
 
-    if (!params.freestash.empty()) {
-        FreeStash(params.stashbase, params.freestash);
-        params.freestash.clear();
-    }
+  if (!params.freestash.empty()) {
+    FreeStash(params.stashbase, params.freestash);
+    params.freestash.clear();
+  }
 
-    params.written += tgt.size;
+  params.written += tgt.size;
 
-    return 0;
+  return 0;
 }
 
 static int PerformCommandErase(CommandParameters& params) {