kernel: lib: Add snprintf() and vsnprintf()

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 123 insertions, 0 deletions

diff --git a/sys/include/lib/string.h b/sys/include/lib/string.h
index d8f6ea2..f4ee93d 100644
--- a/sys/include/lib/string.h
+++ b/sys/include/lib/string.h
@@ -31,6 +31,7 @@
 #define _LIB_STRING_H_
 
 #include <sys/types.h>
+#include <stdarg.h>
 
 size_t strlen(const char *s);
 char *itoa(int64_t value, char *buf, int base);
@@ -41,5 +42,7 @@ void *memset(void *s, int c, size_t n);
 void *memset64(void *s, int c, size_t n);
 int memcmp(const void *s1, const void *s2, size_t n);
 int strcmp(const char *s1, const char *s2);
+int vsnprintf(char *s, size_t size, const char *fmt, va_list ap);
+int snprintf(char *s, size_t size, const char *fmt, ...);
 
 #endif  /* !_LIB_STRING_H_ */
diff --git a/sys/lib/string/vsnprintf.c b/sys/lib/string/vsnprintf.c
new file mode 100644
index 0000000..37ec759
--- /dev/null
+++ b/sys/lib/string/vsnprintf.c
@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <string.h>
+#include <stdarg.h>
+#include <sys/types.h>
+
+static inline void
+printc(char *buf, size_t size, size_t *off, char c)
+{
+    if (*off < size - 1) {
+        buf[(*off)++] = c;
+    }
+    buf[*off] = 0;
+}
+
+static void
+printstr(char *buf, size_t size, size_t *off, const char *s)
+{
+    while (*off < size - 1 && *s != '\0') {
+        buf[(*off)++] = *(s)++;
+    }
+    buf[*off] = 0;
+}
+
+int
+snprintf(char *s, size_t size, const char *fmt, ...)
+{
+    va_list ap;
+    int ret;
+
+    va_start(ap, fmt);
+    ret = vsnprintf(s, size, fmt, ap);
+    va_end(ap);
+    return ret;
+}
+
+int
+vsnprintf(char *s, size_t size, const char *fmt, va_list ap)
+{
+    size_t tmp_len, off = 0;
+    ssize_t num = 0;
+    char c, c1, num_buf[256] = {0};
+    const char *tmp_str;
+
+    while (off < (size - 1)) {
+        while (*fmt && *fmt != '%') {
+            printc(s, size, &off, *fmt++);
+        }
+        if (*(fmt)++ == '\0' || off == size - 1) {
+            return off;
+        }
+
+        c = *fmt++;
+        switch (c) {
+        case 'c':
+            c1 = (char )va_arg(ap, int);
+            printc(s, size, &off, c1);
+            break;
+        case 'd':
+            num = va_arg(ap, int64_t);
+            itoa(num, num_buf, 10);
+            printstr(s, size, &off, num_buf);
+            break;
+        case 'p':
+            num = va_arg(ap, uint64_t);
+            itoa(num, num_buf, 16);
+            tmp_len = strlen(num_buf);
+            /*
+             * Now we pad this.
+             *
+             * XXX TODO: This assumes 64-bits, should be
+             *           cleaned up.
+             */
+            for (size_t i = 0; i < 18 - tmp_len; ++i) {
+                printc(s, size, &off, '0');
+            }
+            printstr(s, size, &off, num_buf + 2);
+            break;
+        case 'x':
+            num = va_arg(ap, uint64_t);
+            itoa(num, num_buf, 16);
+            tmp_len = strlen(num_buf);
+            printstr(s, size, &off, num_buf + 2);
+            break;
+        case 's':
+            tmp_str = va_arg(ap, const char *);
+            printstr(s, size, &off, tmp_str);
+            break;
+        }
+    }
+
+    return 0;
+}