view mercurial/bitmanipulation.h @ 37968:0304f22497fa

revlog: use node tree (native code) for shortest() calculation

I want to rewrite revlog.shortest() to disambiguate only among hex
nodeids and then disambiguate the result with revnums at a higher
level (in scmutil). However, that would slow down `hg log -T
'{shortest(node,1)}\n'` from 5.0s to 6.8s, which I wasn't sure would
be acceptable. So this patch makes revlog.shortest() use the node tree
for finding the length of the shortest prefix that's unambiguous among
nodeids. Once that has been found, it makes it longer until it is also
not ambiguous with a revnum.

This speeds up `hg log -T '{shortest(node,1)}\n'` from 5.0s to 4.0s.

Differential Revision: https://phab.mercurial-scm.org/D3499

#ifndef _HG_BITMANIPULATION_H_
#define _HG_BITMANIPULATION_H_

#include <string.h>

#include "compat.h"

static inline uint32_t getbe32(const char *c)
{
	const unsigned char *d = (const unsigned char *)c;

	return ((d[0] << 24) | (d[1] << 16) | (d[2] << 8) | (d[3]));
}

static inline int16_t getbeint16(const char *c)
{
	const unsigned char *d = (const unsigned char *)c;

	return ((d[0] << 8) | (d[1]));
}

static inline uint16_t getbeuint16(const char *c)
{
	const unsigned char *d = (const unsigned char *)c;

	return ((d[0] << 8) | (d[1]));
}

static inline void putbe32(uint32_t x, char *c)
{
	c[0] = (x >> 24) & 0xff;
	c[1] = (x >> 16) & 0xff;
	c[2] = (x >> 8) & 0xff;
	c[3] = (x)&0xff;
}

static inline double getbefloat64(const char *c)
{
	const unsigned char *d = (const unsigned char *)c;
	double ret;
	int i;
	uint64_t t = 0;
	for (i = 0; i < 8; i++) {
		t = (t << 8) + d[i];
	}
	memcpy(&ret, &t, sizeof(t));
	return ret;
}

#endif