add memmem()

memmem() is a nice GNU extension for searching a length limited string
in another one.

This compat version is based on the version found in glibc 2.2 (GPL 2);
I only removed the optimization of checking the first char by hand, and
generally tried to keep the code simple.  We can add it back if memcmp
shows up high in a profile, but for now I prefer to keep it (almost
trivially) simple.

Since I don't really know which platforms beside those with a glibc
have their own memmem(), I used a heuristic: if NO_STRCASESTR is set,
then NO_MEMMEM is set, too.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Makefile b/Makefile
index 51af531c9a0c23dcd577bc73ccd14940ed20ae57..bae073fe372dd744678502da1973bd5386fc7bd7 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -28,6 +28,8 @@ all::
 #
 # Define NO_STRCASESTR if you don't have strcasestr.
 #
+# Define NO_MEMMEM if you don't have memmem.
+#
 # Define NO_STRLCPY if you don't have strlcpy.
 #
 # Define NO_STRTOUMAX if you don't have strtoumax in the C library.
@@ -402,6 +404,7 @@ ifeq ($(uname_S),SunOS)
        NEEDS_NSL = YesPlease
        SHELL_PATH = /bin/bash
        NO_STRCASESTR = YesPlease
+       NO_MEMMEM = YesPlease
        NO_HSTRERROR = YesPlease
        ifeq ($(uname_R),5.8)
                NEEDS_LIBICONV = YesPlease
@@ -424,6 +427,7 @@ ifeq ($(uname_O),Cygwin)
        NO_D_TYPE_IN_DIRENT = YesPlease
        NO_D_INO_IN_DIRENT = YesPlease
        NO_STRCASESTR = YesPlease
+       NO_MEMMEM = YesPlease
        NO_SYMLINK_HEAD = YesPlease
        NEEDS_LIBICONV = YesPlease
        NO_FAST_WORKING_DIRECTORY = UnfortunatelyYes
@@ -442,6 +446,7 @@ ifeq ($(uname_S),FreeBSD)
 endif
 ifeq ($(uname_S),OpenBSD)
        NO_STRCASESTR = YesPlease
+       NO_MEMMEM = YesPlease
        NEEDS_LIBICONV = YesPlease
        BASIC_CFLAGS += -I/usr/local/include
        BASIC_LDFLAGS += -L/usr/local/lib
@@ -456,6 +461,7 @@ ifeq ($(uname_S),NetBSD)
 endif
 ifeq ($(uname_S),AIX)
        NO_STRCASESTR=YesPlease
+       NO_MEMMEM = YesPlease
        NO_STRLCPY = YesPlease
        NEEDS_LIBICONV=YesPlease
 endif
@@ -467,6 +473,7 @@ ifeq ($(uname_S),IRIX64)
        NO_IPV6=YesPlease
        NO_SETENV=YesPlease
        NO_STRCASESTR=YesPlease
+       NO_MEMMEM = YesPlease
        NO_STRLCPY = YesPlease
        NO_SOCKADDR_STORAGE=YesPlease
        SHELL_PATH=/usr/gnu/bin/bash
@@ -661,6 +668,10 @@ ifdef NO_HSTRERROR
        COMPAT_CFLAGS += -DNO_HSTRERROR
        COMPAT_OBJS += compat/hstrerror.o
 endif
+ifdef NO_MEMMEM
+       COMPAT_CFLAGS += -DNO_MEMMEM
+       COMPAT_OBJS += compat/memmem.o
+endif
 
 ifeq ($(TCLTK_PATH),)
 NO_TCLTK=NoThanks

diff --git a/compat/memmem.c b/compat/memmem.c
new file mode 100644 (file)
index 0000000..cd0d877
--- /dev/null
+++ b/compat/memmem.c
@@ -0,0 +1,29 @@
+#include "../git-compat-util.h"
+
+void *gitmemmem(const void *haystack, size_t haystack_len,
+                const void *needle, size_t needle_len)
+{
+       const char *begin = haystack;
+       const char *last_possible = begin + haystack_len - needle_len;
+
+       /*
+        * The first occurrence of the empty string is deemed to occur at
+        * the beginning of the string.
+        */
+       if (needle_len == 0)
+               return (void *)begin;
+
+       /*
+        * Sanity check, otherwise the loop might search through the whole
+        * memory.
+        */
+       if (haystack_len < needle_len)
+               return NULL;
+
+       for (; begin <= last_possible; begin++) {
+               if (!memcmp(begin, needle, needle_len))
+                       return (void *)begin;
+       }
+
+       return NULL;
+}

diff --git a/git-compat-util.h b/git-compat-util.h
index ca0a597a282328bff9e0e29fd3653dbd656489fb..1bfbdeb94f55d57b429b91aa8762618153c34f7f 100644 (file)
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -172,6 +172,12 @@ extern uintmax_t gitstrtoumax(const char *, char **, int);
 extern const char *githstrerror(int herror);
 #endif
 
+#ifdef NO_MEMMEM
+#define memmem gitmemmem
+void *gitmemmem(const void *haystack, size_t haystacklen,
+                const void *needle, size_t needlelen);
+#endif
+
 extern void release_pack_memory(size_t, int);
 
 static inline char* xstrdup(const char *str)