Mercurial > hg
view mercurial/util.h @ 29322:66dbdd3cc2b9 stable
bdiff: extend matches across popular lines
For very large diffs that have large numbers of identical lines (JSON
dumps) that also have large blocks of identical text, bdiff could become
confused about which block matches which because it can only match
very limited regions. The result is very large diffs for small sets of edits.
The earlier recursion rebalancing fix made this behavior more frequent because
it's now more prone to match block 1 to block 2. One frequent user of
large JSON files reported being unable to pass the resulting diffs
through their code review system.
Prior to this change, bdiff would calculate the length of a match at
(i, j) as 1 + length found at (i-1, j-1). With large number of popular
(ignored) lines, this often meant matches couldn't be extended
backwards at all and thus all matching regions were very small.
Disabling the popularity threshold is not an option because it brings
back quadratic behavior.
Instead, we extend a match backwards until we either found a previously
discovered match or we find a mismatching line. This thus successfully
bridges over any popular lines inside and before a matching region.
The larger regions then significant reduce the probability of confusion.
author | Matt Mackall <mpm@selenic.com> |
---|---|
date | Thu, 02 Jun 2016 17:09:06 -0500 |
parents | 14bf7679fb68 |
children | 284d742e5611 |
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/* util.h - utility functions for interfacing with the various python APIs. This software may be used and distributed according to the terms of the GNU General Public License, incorporated herein by reference. */ #ifndef _HG_UTIL_H_ #define _HG_UTIL_H_ #if PY_MAJOR_VERSION >= 3 #define IS_PY3K #define PyInt_FromLong PyLong_FromLong #define PyInt_AsLong PyLong_AsLong /* Mapping of some of the python < 2.x PyString* functions to py3k's PyUnicode. The commented names below represent those that are present in the PyBytes definitions for python < 2.6 (below in this file) that don't have a direct implementation. */ #define PyStringObject PyUnicodeObject #define PyString_Type PyUnicode_Type #define PyString_Check PyUnicode_Check #define PyString_CheckExact PyUnicode_CheckExact #define PyString_CHECK_INTERNED PyUnicode_CHECK_INTERNED #define PyString_AS_STRING PyUnicode_AsLatin1String #define PyString_GET_SIZE PyUnicode_GET_SIZE #define PyString_FromStringAndSize PyUnicode_FromStringAndSize #define PyString_FromString PyUnicode_FromString #define PyString_FromFormatV PyUnicode_FromFormatV #define PyString_FromFormat PyUnicode_FromFormat /* #define PyString_Size PyUnicode_GET_SIZE */ /* #define PyString_AsString */ /* #define PyString_Repr */ #define PyString_Concat PyUnicode_Concat #define PyString_ConcatAndDel PyUnicode_AppendAndDel #define _PyString_Resize PyUnicode_Resize /* #define _PyString_Eq */ #define PyString_Format PyUnicode_Format /* #define _PyString_FormatLong */ /* #define PyString_DecodeEscape */ #define _PyString_Join PyUnicode_Join #define PyString_Decode PyUnicode_Decode #define PyString_Encode PyUnicode_Encode #define PyString_AsEncodedObject PyUnicode_AsEncodedObject #define PyString_AsEncodedString PyUnicode_AsEncodedString #define PyString_AsDecodedObject PyUnicode_AsDecodedObject #define PyString_AsDecodedString PyUnicode_AsDecodedUnicode /* #define PyString_AsStringAndSize */ #define _PyString_InsertThousandsGrouping _PyUnicode_InsertThousandsGrouping #endif /* PY_MAJOR_VERSION */ #ifdef _WIN32 #ifdef _MSC_VER /* msvc 6.0 has problems */ #define inline __inline typedef signed char int8_t; typedef short int16_t; typedef long int32_t; typedef __int64 int64_t; typedef unsigned char uint8_t; typedef unsigned short uint16_t; typedef unsigned long uint32_t; typedef unsigned __int64 uint64_t; #else #include <stdint.h> #endif #else /* not windows */ #include <sys/types.h> #if defined __BEOS__ && !defined __HAIKU__ #include <ByteOrder.h> #else #include <arpa/inet.h> #endif #include <inttypes.h> #endif #if defined __hpux || defined __SUNPRO_C || defined _AIX #define inline #endif #ifdef __linux #define inline __inline #endif typedef struct { PyObject_HEAD char state; int mode; int size; int mtime; } dirstateTupleObject; extern PyTypeObject dirstateTupleType; #define dirstate_tuple_check(op) (Py_TYPE(op) == &dirstateTupleType) 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; } /* This should be kept in sync with normcasespecs in encoding.py. */ enum normcase_spec { NORMCASE_LOWER = -1, NORMCASE_UPPER = 1, NORMCASE_OTHER = 0 }; #define MIN(a, b) (((a)<(b))?(a):(b)) /* VC9 doesn't include bool and lacks stdbool.h based on my searching */ #if defined(_MSC_VER) || __STDC_VERSION__ < 199901L #define true 1 #define false 0 typedef unsigned char bool; #else #include <stdbool.h> #endif #endif /* _HG_UTIL_H_ */