1 files changed, 111 insertions, 0 deletions
diff --git a/usr/sdk/common/string/itoa.c b/usr/sdk/common/string/itoa.c
new file mode 100644
index 0000000..be04480
--- /dev/null
+++ b/usr/sdk/common/string/itoa.c
@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2025, Ian Moffett.
+ * Provided under the BSD-3 clause.
+ */
+
+#include <sdk/types.h>
+#include <sdk/string.h>
+
+static char *itoa_base10_convert(QUAD value, char *buf);
+
+static char *
+itoa_base10_convert(QUAD value, char *buf)
+{
+    UQUAD i;
+    UBYTE tmp;
+    BOOL is_negative;
+
+    i = 0;
+    is_negative = false;
+
+    if (value == 0) {
+        buf[i++] = '0';
+        buf[i++] = '\0';
+        return buf;
+    }
+
+    if (value < 0) {
+        /* Easier to handle positive numbers */
+        value *= -1;
+        is_negative = true;
+    }
+
+    while (value > 0) {
+        buf[i++] = '0' + (value % 10);
+        value /= 10;
+    }
+
+    if (is_negative) {
+        buf[i++] = '-';
+    }
+
+    buf[i--] = '\0';
+
+    /* Result is in reverse */
+    for (int j = 0; j < i; ++j, --i) {
+        tmp = buf[j];
+        buf[j] = buf[i];
+        buf[i] = tmp;
+    }
+
+    return buf;
+}
+
+static char *
+itoa_convert_base16(UQUAD n, char *buffer)
+{
+    BOOL pad;
+    UBYTE nibble;
+    UBYTE i, j, tmp;
+    const char *ascii_nums = "0123456789ABCDEF";
+
+    i = 0;
+    pad = false;
+
+    if (n == 0) {
+        /* Zero, no need to parse */
+        memcpy(buffer, "0x00\0", 5);
+        return buffer;
+    }
+    /* If one digit, pad out 2 later */
+    if (n < 0x10) {
+        pad = true;
+    }
+
+    while (n > 0) {
+        nibble = (UBYTE)n & 0x0F;
+        nibble = ascii_nums[nibble];
+        buffer[i++] = nibble;
+        n >>= 4;        /* Fetch next nibble */
+    }
+
+    if (pad) {
+        buffer[i++] = '0';
+    }
+
+    /* Add "0x" prefix */
+    buffer[i++] = 'x';
+    buffer[i++] = '0';
+    buffer[i--] = '\0';
+
+    /* Unreverse the result */
+    for (j = 0; j < i; ++j, --i) {
+        tmp = buffer[j];
+        buffer[j] = buffer[i];
+        buffer[i] = tmp;
+    }
+    return buffer;
+}
+
+char *
+itoa(QUAD value, char *buf, int base)
+{
+    switch (base) {
+        case 10:
+            return itoa_base10_convert(value, buf);
+        case 16:
+            return itoa_convert_base16(value, buf);
+        default:
+            return NULL;
+    }
+}