bdiff: don't check border condition in loop
This is pretty much a copy of d500ddae7494, just to a different loop.
The condition `p == plast` (`plast == a + len - 1`) was only true on
the final iteration of the loop. So it was wasteful to check for it
on every iteration. We decrease the iteration count by 1 and add an
explicit check for `p == plast` after the loop.
Again, we see modest wins.
From the mozilla-unified repository:
$ perfbdiff -m 3041e4d59df2
! wall 0.035502 comb 0.040000 user 0.040000 sys 0.000000 (best of 100)
! wall 0.030480 comb 0.030000 user 0.030000 sys 0.000000 (best of 100)
$ perfbdiff 0e9928989e9c --alldata --count 100
! wall 4.097394 comb 4.100000 user 4.100000 sys 0.000000 (best of 3)
! wall 3.597798 comb 3.600000 user 3.600000 sys 0.000000 (best of 3)
The 2nd example throws a total of ~3.3GB of data at bdiff. This
change increases the throughput from ~811 MB/s to ~924 MB/s.
/**
* Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*/
#ifndef ZSTD_ERRORS_H_398273423
#define ZSTD_ERRORS_H_398273423
#if defined (__cplusplus)
extern "C" {
#endif
/*===== dependency =====*/
#include <stddef.h> /* size_t */
/*-****************************************
* error codes list
******************************************/
typedef enum {
ZSTD_error_no_error,
ZSTD_error_GENERIC,
ZSTD_error_prefix_unknown,
ZSTD_error_version_unsupported,
ZSTD_error_parameter_unknown,
ZSTD_error_frameParameter_unsupported,
ZSTD_error_frameParameter_unsupportedBy32bits,
ZSTD_error_frameParameter_windowTooLarge,
ZSTD_error_compressionParameter_unsupported,
ZSTD_error_init_missing,
ZSTD_error_memory_allocation,
ZSTD_error_stage_wrong,
ZSTD_error_dstSize_tooSmall,
ZSTD_error_srcSize_wrong,
ZSTD_error_corruption_detected,
ZSTD_error_checksum_wrong,
ZSTD_error_tableLog_tooLarge,
ZSTD_error_maxSymbolValue_tooLarge,
ZSTD_error_maxSymbolValue_tooSmall,
ZSTD_error_dictionary_corrupted,
ZSTD_error_dictionary_wrong,
ZSTD_error_maxCode
} ZSTD_ErrorCode;
/*! ZSTD_getErrorCode() :
convert a `size_t` function result into a `ZSTD_ErrorCode` enum type,
which can be used to compare directly with enum list published into "error_public.h" */
ZSTD_ErrorCode ZSTD_getErrorCode(size_t functionResult);
const char* ZSTD_getErrorString(ZSTD_ErrorCode code);
#if defined (__cplusplus)
}
#endif
#endif /* ZSTD_ERRORS_H_398273423 */