From 4bc8a39d6c6390d4ebfee6a16e22750e52d3da6a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Sat, 16 May 2026 20:26:37 +0200
Subject: [PATCH] base64: add base64_encode_oneshot()

Convenience function for base64_encode() + base64_encode_final().

Internally, we also add base64_encode_to_buffer()

This is an internal function that encodes a multiple-of-three long
input into a user allocated buffer.

base64_encode() and base64_encode_oneshot() uses the new function to
do the bulk of the encoding. This allows base64_encode_oneshot() to do
a single allocation.

This patch also adds unit tests for both base64_encode() and
base64_encode_oneshot() (but _not_ for base64_encode_final()).

Finally, the type of the 'data' parameter is changed to 'void*'.
---
 base64.c | 124 ++++++++++++++++++++++++++++++++++++++++++++++++-------
 base64.h |   5 ++-
 2 files changed, 113 insertions(+), 16 deletions(-)

diff --git a/base64.c b/base64.c
index db697cb0..4ce62aae 100644
--- a/base64.c
+++ b/base64.c
@@ -10,6 +10,9 @@
 #define LOG_ENABLE_DBG 0
 #include "log.h"
 #include "debug.h"
+#include "macros.h"
+#include "util.h"
+#include "xmalloc.h"
 
 enum {
     P = 1 << 6, // Padding byte (=)
@@ -102,16 +105,16 @@ invalid:
     return NULL;
 }
 
-char *
-base64_encode(const uint8_t *data, size_t size)
+static inline size_t ALWAYS_INLINE
+base64_out_size_for(size_t in_size)
+{
+    return (in_size + 2) / 3 * 4 + 1;  /* +1 since we always NULL terminate */
+}
+
+static size_t
+base64_encode_to_buffer(const uint8_t *data, size_t size, char *out)
 {
     xassert(size % 3 == 0);
-    if (unlikely(size % 3 != 0))
-        return NULL;
-
-    char *ret = malloc(size / 3 * 4 + 1);
-    if (unlikely(ret == NULL))
-        return NULL;
 
     for (size_t i = 0, o = 0; i < size; i += 3, o += 4) {
         int x = data[i + 0];
@@ -130,24 +133,41 @@ base64_encode(const uint8_t *data, size_t size)
         char c2 = lookup[c];
         char c3 = lookup[d];
 
-        ret[o + 0] = c0;
-        ret[o + 1] = c1;
-        ret[o + 2] = c2;
-        ret[o + 3] = c3;
+        out[o + 0] = c0;
+        out[o + 1] = c1;
+        out[o + 2] = c2;
+        out[o + 3] = c3;
 
         LOG_DBG("base64: encode: %c%c%c%c", c0, c1, c2, c3);
     }
 
-    ret[size / 3 * 4] = '\0';
+    const size_t out_len = size / 3 * 4;
+    out[out_len] = '\0';
+    return out_len;
+}
+
+char *
+base64_encode(const void *data, size_t size)
+{
+    if (unlikely(size % 3 != 0))
+        return NULL;
+
+    char *ret = malloc(base64_out_size_for(size));
+    if (unlikely(ret == NULL))
+        return NULL;
+
+    base64_encode_to_buffer(data, size, ret);
     return ret;
 }
 
 void
-base64_encode_final(const uint8_t *data, size_t size, char result[4])
+base64_encode_final(const void *_data, size_t size, char result[4])
 {
     xassert(size > 0);
     xassert(size < 3);
 
+    const uint8_t *data = _data;
+
     uint32_t v = 0;
     if (size >= 1)
         v |= data[0] << 16;
@@ -170,3 +190,79 @@ base64_encode_final(const uint8_t *data, size_t size, char result[4])
 
     LOG_DBG("base64: encode: %c%c%c%c", c0, c1, c2, c3);
 }
+
+char *
+base64_encode_oneshot(const void *data, size_t size)
+{
+    const size_t encoded_size = base64_out_size_for(size);
+
+    char *encoded = malloc(encoded_size);
+    if (unlikely(encoded == NULL))
+        return NULL;
+
+    size_t out_len = base64_encode_to_buffer(data, size / 3 * 3, encoded);
+
+    const size_t remaining = size % 3;
+    if (remaining == 0)
+        return encoded;
+
+    base64_encode_final(&((const uint8_t *)data)[size - remaining],
+                        remaining, &encoded[out_len]);
+    encoded[out_len + 4] = '\0';
+    return encoded;
+}
+
+UNITTEST
+{
+    char *encoded = NULL;
+
+    encoded = base64_encode("", 0);
+    xassert(streq(encoded, ""));
+    free(encoded);
+
+    encoded = base64_encode_oneshot("123", 3);
+    xassert(streq(encoded, "MTIz"));
+    free(encoded);
+
+    encoded = base64_encode_oneshot("123456", 6);
+    xassert(streq(encoded, "MTIzNDU2"));
+    free(encoded);
+}
+
+UNITTEST
+{
+    char *encoded = NULL;
+
+    encoded = base64_encode_oneshot("", 0);
+    xassert(streq(encoded, ""));
+    free(encoded);
+
+    encoded = base64_encode_oneshot("1", 1);
+    xassert(streq(encoded, "MQ=="));
+    free(encoded);
+
+    encoded = base64_encode_oneshot("12", 2);
+    xassert(streq(encoded, "MTI="));
+    free(encoded);
+
+    encoded = base64_encode_oneshot("123", 3);
+    xassert(streq(encoded, "MTIz"));
+    free(encoded);
+
+    encoded = base64_encode_oneshot("1234", 4);
+    xassert(streq(encoded, "MTIzNA=="));
+    free(encoded);
+
+    encoded = base64_encode_oneshot("12345", 5);
+    xassert(streq(encoded, "MTIzNDU="));
+    free(encoded);
+
+    encoded = base64_encode_oneshot("123456", 6);
+    xassert(streq(encoded, "MTIzNDU2"));
+    free(encoded);
+
+    encoded = base64_encode_oneshot("hello world", 11);
+    xassert(streq(encoded, "aGVsbG8gd29ybGQ="));
+    free(encoded);
+
+}
diff --git a/base64.h b/base64.h
index 3fa3d078..13541310 100644
--- a/base64.h
+++ b/base64.h
@@ -4,5 +4,6 @@
 #include <stddef.h>
 
 char *base64_decode(const char *s, size_t *out_len);
-char *base64_encode(const uint8_t *data, size_t size);
-void base64_encode_final(const uint8_t *data, size_t size, char result[4]);
+char *base64_encode(const void *data, size_t size);
+void base64_encode_final(const void *data, size_t size, char result[4]);
+char *base64_encode_oneshot(const void *data, size_t size);