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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/metrics/metrics_hashes.h"
#include <string.h>
#include <string_view>
#include "base/check_op.h"
#include "base/containers/span.h"
#include "base/hash/md5.h"
#include "base/hash/sha1.h"
#include "base/numerics/byte_conversions.h"
namespace base {
namespace {
// Converts the 8-byte prefix of an MD5 hash into a uint64_t value.
inline uint64_t DigestToUInt64(const MD5Digest& digest) {
return U64FromBigEndian(span(digest.a).first<8u>());
}
// Converts the 4-byte prefix of an MD5 hash into a uint32_t value.
inline uint32_t DigestToUInt32(const MD5Digest& digest) {
return U32FromBigEndian(span(digest.a).first<4u>());
}
} // namespace
uint64_t HashMetricName(std::string_view name) {
// Corresponding Python code for quick look up:
//
// import struct
// import hashlib
// struct.unpack('>Q', hashlib.md5(name.encode('utf-8')).digest()[:8])[0]
//
MD5Digest digest;
MD5Sum(as_byte_span(name), &digest);
return DigestToUInt64(digest);
}
uint32_t HashMetricNameAs32Bits(std::string_view name) {
MD5Digest digest;
MD5Sum(as_byte_span(name), &digest);
return DigestToUInt32(digest);
}
uint32_t ParseMetricHashTo32Bits(uint64_t hash) {
return (hash >> 32);
}
uint32_t HashFieldTrialName(std::string_view name) {
// SHA-1 is designed to produce a uniformly random spread in its output space,
// even for nearly-identical inputs.
SHA1Digest sha1_hash = SHA1Hash(as_byte_span(name));
return U32FromLittleEndian(span(sha1_hash).first<4u>());
}
} // namespace base
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