C API. (google#11)

.appveyor.yml

@@ -39,4 +39,5 @@ build_script:
 
 test_script:
   - out\%CONFIGURATION%\crc32c_tests.exe
+  - out\%CONFIGURATION%\crc32c_capi_tests.exe
   - out\%CONFIGURATION%\crc32c_bench.exe

.travis.yml

@@ -54,4 +54,5 @@ before_script:
 
 script:
 - out/crc32c_tests
+- out/crc32c_capi_tests
 - out/crc32c_bench

CMakeLists.txt

@@ -5,6 +5,11 @@
 cmake_minimum_required(VERSION 3.1)
 project(Crc32c VERSION 0.1.0 LANGUAGES C CXX)
 
+# This project can use C11, but will gracefully decay down to C89.
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_C_STANDARD_REQUIRED OFF)
+set(CMAKE_C_EXTENSIONS OFF)
+
 # This project requires C++11.
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
@@ -308,6 +313,20 @@ if(CRC32C_BUILD_TESTS)
   endif(CRC32C_USE_GLOG)
 
   add_test(NAME crc32c_tests COMMAND crc32c_tests)
+
+  add_executable(crc32c_capi_tests "")
+  target_sources(crc32c_capi_tests
+    PRIVATE
+      "${PROJECT_SOURCE_DIR}/src/crc32c_capi_unittest.c"
+  )
+  target_link_libraries(crc32c_capi_tests crc32c)
+
+  # Warnings as errors in Visual Studio for this project's targets.
+  if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+    set_property(TARGET crc32c_capi_tests APPEND PROPERTY COMPILE_OPTIONS "/WX")
+  endif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+
+  add_test(NAME crc32c_capi_tests COMMAND crc32c_capi_tests)
 endif(CRC32C_BUILD_TESTS)
 
 if(CRC32C_BUILD_BENCHMARKS)

include/crc32c/crc32c.h

@@ -1,16 +1,48 @@
-// Copyright 2017 The CRC32C Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file. See the AUTHORS file for names of contributors.
+/* Copyright 2017 The CRC32C Authors. All rights reserved.
+   Use of this source code is governed by a BSD-style license that can be
+   found in the LICENSE file. See the AUTHORS file for names of contributors. */
 
 #ifndef CRC32C_CRC32C_H_
 #define CRC32C_CRC32C_H_
 
-// The API exported by the CRC32C project.
+/* The API exported by the CRC32C project. */
+
+#if defined(__cplusplus)
 
 #include <cstddef>
 #include <cstdint>
 #include <string>
 
+#else  /* !defined(__cplusplus) */
+
+#include <stddef.h>
+#include <stdint.h>
+
+#endif  /* !defined(__cplusplus) */
+
+
+/* The C API. */
+
+#if defined(__cplusplus)
+extern "C" {
+#endif  /* defined(__cplusplus) */
+
+/* Extends "crc" with the CRC32C of "count" bytes in the buffer pointed by
+   "data" */
+uint32_t crc32c_extend(uint32_t crc, const uint8_t* data, size_t count);
+
+/* Computes the CRC32C of "count" bytes in the buffer pointed by "data". */
+uint32_t crc32c_value(const uint8_t* data, size_t count);
+
+#ifdef __cplusplus
+}  /* end extern "C" */
+#endif  /* defined(__cplusplus) */
+
+
+/* The C++ API. */
+
+#if defined(__cplusplus)
+
 namespace crc32c {
 
 // Extends "crc" with the CRC32C of "count" bytes in the buffer pointed by
@@ -48,5 +80,6 @@ inline uint32_t Crc32c(const std::string_view& string_view) {
 
 }  // namespace crc32c
 
+#endif  /* defined(__cplusplus) */
 
 #endif  // CRC32C_CRC32C_H_

src/crc32c.cc

@@ -27,4 +27,13 @@ uint32_t Extend(uint32_t crc, const uint8_t* data, size_t count) {
   return ExtendPortable(crc, data, count);
 }
 
+extern "C" uint32_t crc32c_extend(uint32_t crc, const uint8_t* data,
+                                  size_t count) {
+  return crc32c::Extend(crc, data, count);
+}
+
+extern "C" uint32_t crc32c_value(const uint8_t* data, size_t count) {
+  return crc32c::Crc32c(data, count);
+}
+
 }  // namespace crc32c

src/crc32c_capi_unittest.c

@@ -0,0 +1,66 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "crc32c/crc32c.h"
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main() {
+  /* From rfc3720 section B.4. */
+  uint8_t buf[32];
+
+  memset(buf, 0, sizeof(buf));
+  if ((uint32_t)0x8a9136aa != crc32c_value(buf, sizeof(buf))) {
+    printf("crc32c_value(zeros) test failed\n");
+    return 1;
+  }
+
+  memset(buf, 0xff, sizeof(buf));
+  if ((uint32_t)0x62a8ab43 != crc32c_value(buf, sizeof(buf))) {
+    printf("crc32c_value(0xff) test failed\n");
+    return 1;
+  }
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = (uint8_t)i;
+  if ((uint32_t)0x46dd794e != crc32c_value(buf, sizeof(buf))) {
+    printf("crc32c_value(0..31) test failed\n");
+    return 1;
+  }
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = (uint8_t)(31 - i);
+  if ((uint32_t)0x113fdb5c != crc32c_value(buf, sizeof(buf))) {
+    printf("crc32c_value(31..0) test failed\n");
+    return 1;
+  }
+
+  uint8_t data[48] = {
+      0x01, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00,
+      0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x18, 0x28, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  };
+  if ((uint32_t)0xd9963a56 != crc32c_value(data, sizeof(data))) {
+    printf("crc32c_value(31..0) test failed\n");
+    return 1;
+  }
+
+  const uint8_t* hello_space_world = (const uint8_t*)"hello world";
+  const uint8_t* hello_space = (const uint8_t*)"hello ";
+  const uint8_t* world = (const uint8_t*)"world";
+
+  if (crc32c_value(hello_space_world, 11) !=
+      crc32c_extend(crc32c_value(hello_space, 6), world, 5)) {
+    printf("crc32c_extend test failed\n");
+    return 1;
+  }
+
+  printf("All tests passed\n");
+  return 0;
+}