added base64 encoder/decoder

src/base64.c

@@ -0,0 +1,108 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "base64.h"
+
+static unsigned char charTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+static unsigned char inverseTable[256];
+
+__attribute__((constructor)) static void buildInverseTable() {
+	memset(inverseTable, 0x80, 256);
+
+	size_t tableLength = strlen(charTable);
+	for (unsigned int i = 0; i < tableLength; i++) {
+		inverseTable[charTable[i]] = i;
+	}
+	inverseTable['='] = 0;
+}
+
+char* base64_encode(const char* decoded) {
+	size_t length = strlen(decoded) * 4 / 3 + 4;
+	char* encoded = malloc(length + 1);
+	if (encoded == NULL) {
+		return encoded;
+	}
+	
+	size_t i = 0, j = 0;
+	
+	while(length - j >= 3) {
+		encoded[j++] = charTable[  decoded[i + 0] >> 2];
+		encoded[j++] = charTable[((decoded[i + 0] & 0x03) << 4) | (decoded[i + 1] >> 4)];
+		encoded[j++] = charTable[((decoded[i + 1] & 0x0f) << 2) | (decoded[i + 2] >> 6)];
+		encoded[j++] = charTable[  decoded[i + 2] & 0x3f];
+		i += 3;
+	}
+	
+	if (length - j > 0) {
+		encoded[j++] = charTable[decoded[i] >> 2];
+		if (length - i == 1) {
+			encoded[j++] = charTable[(decoded[i] & 0x03) << 4];
+			encoded[j++] = '=';
+		} else {
+			encoded[j++] = charTable[((decoded[i] & 0x03) << 4) | (decoded[i + 1] >> 4)];
+			encoded[j++] = charTable[(decoded[i + 1] & 0x0f) << 2];
+		}
+		encoded[j++] = '=';
+	}
+	
+	encoded[j++] = '\0';
+	
+	return encoded;
+}
+
+char* base64_decode(const char* encoded) {
+	size_t length = strlen(encoded);
+	size_t count = 0;
+	
+	for (size_t i = 0; i < length; i++) {
+		if (inverseTable[encoded[i]] != 0x80) {
+			count++;
+		}
+	}
+	
+	if (count == 0 || count % 4 != 0) {
+		return NULL;
+	}
+	
+	char* decoded = malloc(count / 4 * 3);
+	if (decoded == NULL) {
+		return NULL;
+	}
+	
+	int pad = 0;
+	unsigned char block[4];
+	
+	count = 0;
+	for (size_t i = 0, j = 0; i < length; i++) {
+		unsigned char tmp = inverseTable[encoded[i]];
+		if (tmp == 0x80) {
+			continue;
+		}
+		
+		if (encoded[i] == '=') {
+			pad++;
+		}
+		
+		block[count++] = tmp;
+		if (count == 4) {
+			decoded[j++] = (block[0] << 2) | (block[1] >> 4);
+			decoded[j++] = (block[1] << 4) | (block[2] >> 2);
+			decoded[j++] = (block[2] << 6) | (block[3]);
+			count = 0;
+			if (pad == 1) {
+				j--;
+				break;
+			} else if (pad == 2) {
+				j -= 2;
+				break;
+			} else if (pad > 0) {
+				free(decoded);
+				return NULL;
+			}
+		}
+	}
+	
+	return decoded;
+}

src/base64.h

@@ -0,0 +1,7 @@
+#ifndef BASE64_H_
+#define BASE64_H_
+
+char* base64_encode(const char*);
+char* base64_decode(const char*);
+
+#endif