Add serd_node_new_blob and serd_base64_decode for handling arbitrary binary

data via base64 encoding.


git-svn-id: http://svn.drobilla.net/serd/trunk@280 490d8e77-9747-427b-9fa3-0b8f29cee8a0

3 files changed, 94 insertions, 0 deletions

diff --git a/src/node.c b/src/node.c
index 4628be99..6a27beb7 100644
--- a/src/node.c
+++ b/src/node.c
@@ -218,6 +218,48 @@ serd_node_new_integer(long i)
 	return node;
 }
 
+/**
+   Base64 encoding table.
+   @see <a href="http://tools.ietf.org/html/rfc3548#section-3">RFC3986 S3</a>.
+*/
+static const uint8_t b64_map[64] =
+	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+/**
+   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)'=');
+}
+
+SERD_API
+SerdNode
+serd_node_new_blob(const void* buf, size_t size, bool wrap_lines)
+{
+	const size_t len  = ((size + 2) / 3) * 4 + (wrap_lines ? (size / 57) : 0);
+	SerdNode     node = { calloc(1, len + 2), len, len, 0, SERD_LITERAL };
+	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) {
+			((uint8_t*)node.buf)[j++] = '\n';
+			node.flags |= SERD_HAS_NEWLINE;
+		}
+
+		encode_chunk((uint8_t*)node.buf + j, in, n_in);
+	}
+	return node;
+}
+
 SERD_API
 void
 serd_node_free(SerdNode* node)
diff --git a/src/serd_internal.h b/src/serd_internal.h
index d81d0b34..9af3ae5f 100644
--- a/src/serd_internal.h
+++ b/src/serd_internal.h
@@ -219,4 +219,10 @@ is_space(const char c)
 	}
 }
 
+static inline bool
+is_base64(const uint8_t c)
+{
+	return is_alpha(c) || is_digit(c) || c == '+' || c == '/' || c == '=';
+}
+
 #endif  // SERD_INTERNAL_H
diff --git a/src/string.c b/src/string.c
index 968a20e1..a97c6f98 100644
--- a/src/string.c
+++ b/src/string.c
@@ -112,3 +112,49 @@ serd_strtod(const char* str, char** endptr)
 	*endptr = (char*)s;
 	return result * sign;
 }
+
+/**
+   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[255] =
+	"$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$m$$$ncdefghijkl$$$$$$"
+	"$/0123456789:;<=>?@ABCDEFGH$$$$$$IJKLMNOPQRSTUVWXYZ[\\]^_`ab$$$$"
+	"$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$"
+	"$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$";
+
+static inline uint8_t unmap(const uint8_t in) { return 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] != '='));
+}
+
+SERD_API
+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[4] = "====";
+		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;
+}