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[lib/c] Add bsearch()

--- a/lib/c/src/Makefile

+++ b/lib/c/src/Makefile

@@ -9,6 +9,7 @@

       isalnum.o isalpha.o isascii.o isblank.o iscntrl.o isdigit.o \

       isgraph.o islower.o isprint.o ispunct.o isspace.o isupper.o \

       isxdigit.o toupper.o tolower.o ctype.o setlocale.o \

+      bsearch.o \

       printf.o fprintf.o vfprintf.o \

       fgets.o gets.of fgetc.o fputc.o getchar.o putchar.o \

       fputs.o puts.o fread.o fwrite.o \

--- /dev/null

+++ b/lib/c/src/bsearch.c

@@ -1,0 +1,27 @@

+

+#include <stdlib.h>

+

+void *

+bsearch(const void *key, const void *ary, size_t n, size_t size,

+        int (*cmp)(const void *, const void *))

+{

+	int t;

+	size_t mid, low, high;

+	const char *cur, *base = ary;

+

+	low = 0;

+	high = n - 1;

+	while (low <= high) {

+		mid = low + (high - low) / 2;

+		cur = base + mid*size;

+

+		if ((t == (*cmp)(key, cur)) == 0)

+			return (void *) cur;

+		else if (t > 0)

+			low = mid + 1;

+		else

+			high = mid - 1;

+	}

+

+	return NULL;

+}