Separate base64 implementation

1 files changed, 124 insertions, 0 deletions

diff --git a/src/base64.c b/src/base64.c
new file mode 100644
index 00000000..763c2d2e
--- /dev/null
+++ b/src/base64.c
@@ -0,0 +1,124 @@
+/*
+  Copyright 2011-2020 David Robillard <http://drobilla.net>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#include "base64.h"
+
+#include "serd_internal.h"
+#include "string_utils.h"
+
+#include "serd/serd.h"
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+/**
+   Base64 encoding table.
+
+   @see <a href="http://tools.ietf.org/html/rfc3548#section-3">RFC3548 S3</a>.
+*/
+static const uint8_t b64_map[] =
+	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+/**
+   Base64 decoding table.
+
+   This is indexed by encoded characters and returns the numeric value used
+   for decoding, shifted up by 47 to be in the range of printable ASCII.
+   A '$' is a placeholder for characters not in the base64 alphabet.
+*/
+static const char b64_unmap[] =
+	"$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$m$$$ncdefghijkl$$$$$$"
+	"$/0123456789:;<=>?@ABCDEFGH$$$$$$IJKLMNOPQRSTUVWXYZ[\\]^_`ab$$$$"
+	"$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$"
+	"$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$";
+
+/** Encode 3 raw bytes to 4 base64 characters. */
+static inline void
+encode_chunk(uint8_t out[4], const uint8_t in[3], size_t n_in)
+{
+	out[0] = b64_map[in[0] >> 2];
+	out[1] = b64_map[((in[0] & 0x03) << 4) | ((in[1] & 0xF0) >> 4)];
+	out[2] = ((n_in > 1)
+	          ? (b64_map[((in[1] & 0x0F) << 2) | ((in[2] & 0xC0) >> 6)])
+	          : (uint8_t)'=');
+	out[3] = ((n_in > 2) ? b64_map[in[2] & 0x3F] : (uint8_t)'=');
+}
+
+size_t
+serd_base64_get_length(const size_t size, const bool wrap_lines)
+{
+	return (size + 2) / 3 * 4 + (wrap_lines * ((size - 1) / 57));
+}
+
+bool
+serd_base64_encode(uint8_t* const    str,
+                   const void* const buf,
+                   const size_t      size,
+                   const bool        wrap_lines)
+{
+	bool           has_newline = false;
+	for (size_t i = 0, j = 0; i < size; i += 3, j += 4) {
+		uint8_t in[4] = { 0, 0, 0, 0 };
+		size_t  n_in  = MIN(3, size - i);
+		memcpy(in, (const uint8_t*)buf + i, n_in);
+
+		if (wrap_lines && i > 0 && (i % 57) == 0) {
+			str[j++]    = '\n';
+			has_newline = true;
+		}
+
+		encode_chunk(str + j, in, n_in);
+	}
+
+	return has_newline;
+}
+
+static inline uint8_t
+unmap(const uint8_t in)
+{
+	return (uint8_t)(b64_unmap[in] - 47);
+}
+
+/** Decode 4 base64 characters to 3 raw bytes. */
+static inline size_t
+decode_chunk(const uint8_t in[4], uint8_t out[3])
+{
+	out[0] = (uint8_t)(((unmap(in[0]) << 2))        | unmap(in[1]) >> 4);
+	out[1] = (uint8_t)(((unmap(in[1]) << 4) & 0xF0) | unmap(in[2]) >> 2);
+	out[2] = (uint8_t)(((unmap(in[2]) << 6) & 0xC0) | unmap(in[3]));
+	return 1 + (in[2] != '=') + ((in[2] != '=') && (in[3] != '='));
+}
+
+void*
+serd_base64_decode(const uint8_t* str, size_t len, size_t* size)
+{
+	void* buf = malloc((len * 3) / 4 + 2);
+	*size     = 0;
+	for (size_t i = 0, j = 0; i < len; j += 3) {
+		uint8_t in[] = "====";
+		size_t  n_in = 0;
+		for (; i < len && n_in < 4; ++n_in) {
+			for (; i < len && !is_base64(str[i]); ++i) {} // Skip junk
+			in[n_in] = str[i++];
+		}
+		if (n_in > 1) {
+			*size += decode_chunk(in, (uint8_t*)buf + j);
+		}
+	}
+	return buf;
+}