Add OpenSSL BIO method that writes to a std::string.

crypto/openssl_bio_string.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "crypto/openssl_bio_string.h"
+
+#include <openssl/bio.h>
+#include <string.h>
+
+namespace crypto {
+
+namespace {
+
+int bio_string_write(BIO* bio, const char* data, int len) {
+  reinterpret_cast<std::string*>(bio->ptr)->append(data, len);
+  return len;
+}
+
+int bio_string_puts(BIO* bio, const char* data) {
+  // Note: unlike puts(), BIO_puts does not add a newline.
+  return bio_string_write(bio, data, strlen(data));
+}
+
+long bio_string_ctrl(BIO* bio, int cmd, long num, void* ptr) {
+  std::string* str = reinterpret_cast<std::string*>(bio->ptr);
+  switch (cmd) {
+    case BIO_CTRL_RESET:
+      str->clear();
+      return 1;
+    case BIO_C_FILE_SEEK:
+      return -1;
+    case BIO_C_FILE_TELL:
+      return str->size();
+    case BIO_CTRL_FLUSH:
+      return 1;
+    default:
+      return 0;
+  }
+}
+
+int bio_string_new(BIO* bio) {
+  bio->ptr = NULL;
+  bio->init = 0;
+  return 1;
+}
+
+int bio_string_free(BIO* bio) {
+  // The string is owned by the caller, so there's nothing to do here.
+  return bio != NULL;
+}
+
+BIO_METHOD bio_string_methods = {
+    // TODO(mattm): Should add some type number too? (bio.h uses 1-24)
+    BIO_TYPE_SOURCE_SINK,
+    "bio_string",
+    bio_string_write,
+    NULL, /* read */
+    bio_string_puts,
+    NULL, /* gets */
+    bio_string_ctrl,
+    bio_string_new,
+    bio_string_free,
+    NULL, /* callback_ctrl */
+};
+
+}  // namespace
+
+BIO* BIO_new_string(std::string* out) {
+  BIO* bio = BIO_new(&bio_string_methods);
+  if (!bio)
+    return bio;
+  bio->ptr = out;
+  bio->init = 1;
+  return bio;
+}
+
+}  // namespace crypto