Very first cut at a klibc-derived C library for com32

1 files changed, 44 insertions, 0 deletions

diff --git a/com32/lib/memmem.c b/com32/lib/memmem.c
new file mode 100644
index 00000000..0f59938f
--- /dev/null
+++ b/com32/lib/memmem.c
@@ -0,0 +1,44 @@
+/*
+ * memmem.c
+ *
+ * Find a byte string inside a longer byte string
+ *
+ * This uses the "Not So Naive" algorithm, a very simple but
+ * usually effective algorithm, see:
+ *
+ * http://www-igm.univ-mlv.fr/~lecroq/string/
+ */
+
+#include <string.h>
+
+void *memmem(const void *haystack, size_t n, const void *needle, size_t m)
+{
+  const unsigned char *y = (const unsigned char *)haystack;
+  const unsigned char *x = (const unsigned char *)needle;
+
+  size_t j, k, l;
+
+  if ( m > n )
+    return NULL;
+
+  if ( x[0] == x[1] ) {
+    k = 2;
+    l = 1;
+  } else {
+    k = 1;
+    l = 2;
+  }
+
+  j = 0;
+  while ( j <= n-m ) {
+    if (x[1] != y[j+1]) {
+      j += k;
+    } else {
+      if ( !memcmp(x+2, y+j+2, m-2) && x[0] == y[j] )
+	return (void *)&y[j];
+      j += l;
+    }
+  }
+
+  return NULL;
+}