1 files changed, 209 insertions, 0 deletions
diff --git a/tools/src/string.c b/tools/src/string.c
new file mode 100644
index 0000000..318d0fc
--- /dev/null
+++ b/tools/src/string.c
@@ -0,0 +1,209 @@
+/* SPDX-License-Identifier: MIT */
+
+#include <stdbool.h>
+
+#include "string.h"
+
+// Routines based on The Public Domain C Library
+
+void *memcpy(void *s1, const void *s2, size_t n)
+{
+    char *dest = (char *)s1;
+    const char *src = (const char *)s2;
+
+    while (n--) {
+        *dest++ = *src++;
+    }
+
+    return s1;
+}
+
+void *memmove(void *s1, const void *s2, size_t n)
+{
+    char *dest = (char *)s1;
+    const char *src = (const char *)s2;
+
+    if (dest <= src) {
+        while (n--) {
+            *dest++ = *src++;
+        }
+    } else {
+        src += n;
+        dest += n;
+
+        while (n--) {
+            *--dest = *--src;
+        }
+    }
+
+    return s1;
+}
+
+int memcmp(const void *s1, const void *s2, size_t n)
+{
+    const unsigned char *p1 = (const unsigned char *)s1;
+    const unsigned char *p2 = (const unsigned char *)s2;
+
+    while (n--) {
+        if (*p1 != *p2) {
+            return *p1 - *p2;
+        }
+
+        ++p1;
+        ++p2;
+    }
+
+    return 0;
+}
+
+void *memset(void *s, int c, size_t n)
+{
+    unsigned char *p = (unsigned char *)s;
+
+    while (n--) {
+        *p++ = (unsigned char)c;
+    }
+
+    return s;
+}
+
+void *memchr(const void *s, int c, size_t n)
+{
+    const unsigned char *p = (const unsigned char *)s;
+
+    while (n--) {
+        if (*p == (unsigned char)c) {
+            return (void *)p;
+        }
+
+        ++p;
+    }
+
+    return NULL;
+}
+
+char *strcpy(char *s1, const char *s2)
+{
+    char *rc = s1;
+
+    while ((*s1++ = *s2++)) {
+        /* EMPTY */
+    }
+
+    return rc;
+}
+
+char *strncpy(char *s1, const char *s2, size_t n)
+{
+    char *rc = s1;
+
+    while (n && (*s1++ = *s2++)) {
+        /* Cannot do "n--" in the conditional as size_t is unsigned and we have
+           to check it again for >0 in the next loop below, so we must not risk
+           underflow.
+        */
+        --n;
+    }
+
+    /* Checking against 1 as we missed the last --n in the loop above. */
+    while (n-- > 1) {
+        *s1++ = '\0';
+    }
+
+    return rc;
+}
+
+int strcmp(const char *s1, const char *s2)
+{
+    while ((*s1) && (*s1 == *s2)) {
+        ++s1;
+        ++s2;
+    }
+
+    return (*(unsigned char *)s1 - *(unsigned char *)s2);
+}
+
+int strncmp(const char *s1, const char *s2, size_t n)
+{
+    while (n && *s1 && (*s1 == *s2)) {
+        ++s1;
+        ++s2;
+        --n;
+    }
+
+    if (n == 0) {
+        return 0;
+    } else {
+        return (*(unsigned char *)s1 - *(unsigned char *)s2);
+    }
+}
+
+size_t strlen(const char *s)
+{
+    size_t rc = 0;
+
+    while (s[rc]) {
+        ++rc;
+    }
+
+    return rc;
+}
+
+size_t strnlen(const char *s, size_t n)
+{
+    size_t rc = 0;
+
+    while (rc < n && s[rc]) {
+        ++rc;
+    }
+
+    return rc;
+}
+
+char *strchr(const char *s, int c)
+{
+    do {
+        if (*s == (char)c) {
+            return (char *)s;
+        }
+    } while (*s++);
+
+    return NULL;
+}
+
+char *strrchr(const char *s, int c)
+{
+    size_t i = 0;
+
+    while (s[i++]) {
+        /* EMPTY */
+    }
+
+    do {
+        if (s[--i] == (char)c) {
+            return (char *)s + i;
+        }
+    } while (i);
+
+    return NULL;
+}
+
+/* Very naive, no attempt to check for errors */
+long atol(const char *s)
+{
+    long val = 0;
+    bool neg = false;
+
+    if (*s == '-') {
+        neg = true;
+        s++;
+    }
+
+    while (*s >= '0' && *s <= '9')
+        val = (val * 10) + (*s++ - '0');
+
+    if (neg)
+        val = -val;
+
+    return val;
+}