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Diffstat (limited to 'libc/string/i386/strncat.c')
-rw-r--r--libc/string/i386/strncat.c73
1 files changed, 49 insertions, 24 deletions
diff --git a/libc/string/i386/strncat.c b/libc/string/i386/strncat.c
index 3872679d5..640b0d213 100644
--- a/libc/string/i386/strncat.c
+++ b/libc/string/i386/strncat.c
@@ -32,30 +32,55 @@
#include <string.h>
-/* Experimentally off - libc_hidden_proto(strncat) */
-char *strncat(char * dest,
- const char * src, size_t count)
+#undef strncat
+//#define strncat TESTING
+char *strncat(char * dest, const char * src, size_t count)
{
- int d0, d1, d2, d3;
- __asm__ __volatile__(
- "repne\n\t"
- "scasb\n\t"
- "decl %1\n\t"
- "movl %8,%3\n"
- "incl %3\n"
- "1:\tdecl %3\n\t"
- "jz 2f\n"
- "lodsb\n\t"
- "stosb\n\t"
- "testb %%al,%%al\n\t"
- "jne 1b\n"
- "jmp 3f\n"
- "2:\txorl %2,%2\n\t"
- "stosb\n"
- "3:"
- : "=&S" (d0), "=&D" (d1), "=&a" (d2), "=&c" (d3)
- : "0" (src),"1" (dest),"2" (0),"3" (0xffffffff), "g" (count)
- : "memory");
- return dest;
+ int esi, edi, eax, ecx, edx;
+ __asm__ __volatile__(
+ " xorl %%eax, %%eax\n"
+ " incl %%edx\n"
+ " pushl %%edi\n" /* save dest */
+ " repne; scasb\n"
+ " decl %%edi\n" /* edi => NUL in dest */
+ /* count-- */
+ "1: decl %%edx\n"
+ /* if count reached 0, store NUL and bail out */
+ " movl %%edx, %%eax\n"
+ " jz 2f\n"
+ /* else copy a char */
+ " lodsb\n"
+ "2: stosb\n"
+ " testb %%al, %%al\n"
+ " jnz 1b\n"
+ /* end of loop */
+ " popl %%eax\n" /* restore dest into eax */
+ : "=&S" (esi), "=&D" (edi), "=&a" (eax), "=&c" (ecx), "=&d" (edx)
+ : "0" (src), "1" (dest), "3" (0xffffffff), "4" (count)
+ : "memory"
+ );
+ return (char *)eax;
}
+#ifndef strncat
libc_hidden_def(strncat)
+#else
+/* Uncomment TESTING, gcc -m32 -Os strncat.c -o strncat
+ * and run ./strncat
+ */
+int main()
+{
+ char buf[99];
+
+ strcpy(buf, "abc"); buf[4] = '*'; strncat(buf, "def", 0);
+ printf(strcmp(buf, "abc") == 0 && buf[4] == '*' ? "ok\n" : "BAD!\n");
+
+ strcpy(buf, "abc"); buf[6] = 1; buf[7] = '*'; strncat(buf, "def", 50);
+ printf(strcmp(buf, "abcdef") == 0 && buf[7] == '*' ? "ok\n" : "BAD!\n");
+
+ strcpy(buf, "abc"); buf[6] = 1; buf[7] = '*'; strncat(buf, "def", -1);
+ printf(strcmp(buf, "abcdef") == 0 && buf[7] == '*' ? "ok\n" : "BAD!\n");
+
+ strcpy(buf, "abc"); buf[6] = 1; buf[7] = '*'; strncat(buf, "def123", 3);
+ printf(strcmp(buf, "abcdef") == 0 && buf[7] == '*' ? "ok\n" : "BAD!\n");
+}
+#endif