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// Copyright (c) 2010 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.
#ifndef BASE_OPENNSSL_UTIL_H_
#define BASE_OPENNSSL_UTIL_H_
#pragma once
#include "base/basictypes.h"
namespace base {
// Provides a buffer of at least MIN_SIZE bytes, for use when calling OpenSSL's
// SHA256, HMAC, etc functions, adapting the buffer sizing rules to meet those
// of the our base wrapper APIs.
// This allows the library to write directly to the caller's buffer if it is of
// sufficient size, but if not it will write to temporary |min_sized_buffer_|
// of required size and then its content is automatically copied out on
// destruction, with truncation as appropriate.
template<int MIN_SIZE>
class ScopedOpenSSLSafeSizeBuffer {
public:
ScopedOpenSSLSafeSizeBuffer(unsigned char* output, size_t output_len)
: output_(output),
output_len_(output_len) {
}
~ScopedOpenSSLSafeSizeBuffer() {
if (output_len_ < MIN_SIZE) {
// Copy the temporary buffer out, truncating as needed.
memcpy(output_, min_sized_buffer_, output_len_);
}
// else... any writing already happened directly into |output_|.
}
unsigned char* safe_buffer() {
return output_len_ < MIN_SIZE ? min_sized_buffer_ : output_;
}
private:
// Pointer to the caller's data area and it's associated size, where data
// written via safe_buffer() will [eventually] end up.
unsigned char* output_;
size_t output_len_;
// Temporary buffer writen into in the case where the caller's
// buffer is not of sufficient size.
unsigned char min_sized_buffer_[MIN_SIZE];
};
} // namespace base
#endif // BASE_NSS_UTIL_H_
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