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Fix encoder compilation error on MSVS 2010.

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As reported by @anthrotype, log2() is missing from MSVS 2010.
This patch uses log() and a multiplication in FastLog2()
for _MSV_VER <= 1600 and uses FastLog2() in literal_cost.cc
instead of log2().
This commit is contained in:
Zoltan Szabadka 2015-02-27 16:04:43 +01:00
parent e60b7b846a
commit fab601e81f
2 changed files with 10 additions and 2 deletions
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7
enc/fast_log.h
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@ -164,7 +164,14 @@ static inline double FastLog2(int v) {
if (v < (int)(sizeof(kLog2Table) / sizeof(kLog2Table[0]))) {
return kLog2Table[v];
}
#if defined(_MSC_VER) && _MSC_VER <= 1600
// Visual Studio 2010 does not have the log2() function defined, so we use
// log() and a multiplication instead.
static const double kLog2Inv = 1.4426950408889634f;
return log(static_cast<double>(v)) * kLog2Inv;
#else
return log2(static_cast<double>(v));
#endif
}
} // namespace brotli

5
enc/literal_cost.cc
View File

@ -20,6 +20,8 @@
#include <stdint.h>
#include <algorithm>
#include "./fast_log.h"
namespace brotli {
static int UTF8Position(int last, int c, int clamp) {
@ -111,8 +113,7 @@ void EstimateBitCostsForLiteralsUTF8(size_t pos, size_t len, size_t mask,
if (histo == 0) {
histo = 1;
}
float lit_cost = log2(static_cast<double>(in_window_utf8[utf8_pos])
/ histo);
float lit_cost = FastLog2(in_window_utf8[utf8_pos]) - FastLog2(histo);
lit_cost += 0.02905;
if (lit_cost < 1.0) {
lit_cost *= 0.5;