[2/6] Add base64 encoder/decoder

diff --git a/Makefile.objs b/Makefile.objs
index d1f3e5d..41febf6 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -2,7 +2,7 @@ 
 # QObject
 qobject-obj-y = qint.o qstring.o qdict.o qlist.o qfloat.o qbool.o
 qobject-obj-y += qjson.o json-lexer.o json-streamer.o json-parser.o
-qobject-obj-y += qerror.o error.o
+qobject-obj-y += qerror.o error.o base64.o
 
 #######################################################################
 # oslib-obj-y is code depending on the OS (win32 vs posix)
diff --git a/base64.c b/base64.c
new file mode 100644
index 0000000..f24d039
--- /dev/null
+++ b/base64.c
@@ -0,0 +1,202 @@ 
+/*
+ * Base64 encoder/decoder conforming to RFC 4648
+ * (based on Mozilla's nsprpub/lib/libc/src/base64.c)
+ *
+ * Copyright (C) 2010 Siemens AG
+ *
+ * Authors:
+ *  Jan Kiszka <jan.kiszka@siemens.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#include <inttypes.h>
+#include "base64.h"
+
+static const char base[] =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+static void encode3to4(const uint8_t *src, char *dest)
+{
+    uint32_t b32 = 0;
+    int i, j = 18;
+
+    for (i = 0; i < 3; i++) {
+        b32 <<= 8;
+        b32 |= src[i];
+    }
+    for (i = 0; i < 4; i++) {
+        dest[i] = base[(b32 >> j) & 0x3F];
+        j -= 6;
+    }
+}
+
+static void encode2to4(const uint8_t *src, char *dest)
+{
+    dest[0] = base[(src[0] >> 2) & 0x3F];
+    dest[1] = base[((src[0] & 0x03) << 4) | ((src[1] >> 4) & 0x0F)];
+    dest[2] = base[(src[1] & 0x0F) << 2];
+    dest[3] = '=';
+}
+
+static void encode1to4(const uint8_t *src, char *dest)
+{
+    dest[0] = base[(src[0] >> 2) & 0x3F];
+    dest[1] = base[(src[0] & 0x03) << 4];
+    dest[2] = '=';
+    dest[3] = '=';
+}
+
+/*
+ * Encode data in 'src' of length 'srclen' to a base64 string, saving the
+ * null-terminated result in 'dest'. The size of the destition buffer must be
+ * at least ((srclen + 2) / 3) * 4 + 1.
+ */
+void base64_encode(const uint8_t *src, size_t srclen, char *dest)
+{
+    while (srclen >= 3) {
+        encode3to4(src, dest);
+        src += 3;
+        dest += 4;
+        srclen -= 3;
+    }
+    switch (srclen) {
+    case 2:
+        encode2to4(src, dest);
+        dest += 4;
+        break;
+    case 1:
+        encode1to4(src, dest);
+        dest += 4;
+        break;
+    case 0:
+        break;
+    }
+    dest[0] = 0;
+}
+
+static int32_t codetovalue(char c)
+{
+    if (c >= 'A' && c <= 'Z') {
+        return c - 'A';
+    } else if (c >= 'a' && c <= 'z') {
+        return c - 'a' + 26;
+    } else if (c >= '0' && c <= '9') {
+        return c - '0' + 52;
+    } else if (c == '+') {
+        return 62;
+    } else if (c == '/') {
+        return 63;
+    } else {
+        return -1;
+    }
+}
+
+static int decode4to3(const char *src, uint8_t *dest)
+{
+    uint32_t b32 = 0;
+    int32_t bits;
+    int i;
+
+    for (i = 0; i < 4; i++) {
+        bits = codetovalue(src[i]);
+        if (bits < 0) {
+            return bits;
+        }
+        b32 <<= 6;
+        b32 |= bits;
+    }
+    dest[0] = (b32 >> 16) & 0xFF;
+    dest[1] = (b32 >> 8) & 0xFF;
+    dest[2] = b32 & 0xFF;
+
+    return 0;
+}
+
+static int decode3to2(const char *src, uint8_t *dest)
+{
+    uint32_t b32 = 0;
+    int32_t bits;
+
+    bits = codetovalue(src[0]);
+    if (bits < 0) {
+        return bits;
+    }
+    b32 = (uint32_t)bits;
+    b32 <<= 6;
+
+    bits = codetovalue(src[1]);
+    if (bits < 0) {
+        return bits;
+    }
+    b32 |= (uint32_t)bits;
+    b32 <<= 4;
+
+    bits = codetovalue(src[2]);
+    if (bits < 0) {
+        return bits;
+    }
+    b32 |= ((uint32_t)bits) >> 2;
+
+    dest[0] = (b32 >> 8) & 0xFF;
+    dest[1] = b32 & 0xFF;
+
+    return 0;
+}
+
+static int decode2to1(const char *src, uint8_t *dest)
+{
+    uint32_t b32;
+    int32_t bits;
+
+    bits = codetovalue(src[0]);
+    if (bits < 0) {
+        return bits;
+    }
+    b32 = (uint32_t)bits << 2;
+
+    bits = codetovalue(src[1]);
+    if (bits < 0) {
+        return bits;
+    }
+    b32 |= ((uint32_t)bits) >> 4;
+
+    dest[0] = b32;
+
+    return 0;
+}
+
+/*
+ * Convert string 'src' of length 'srclen' from base64 to binary form,
+ * saving the result in 'dest'. The size of the destination buffer must be at
+ * least srclen * 3 / 4.
+ *
+ * Returns 0 on success, -1 on conversion error.
+ */
+int base64_decode(const char *src, size_t srclen, uint8_t *dest)
+{
+    int ret;
+
+    while (srclen >= 4) {
+        ret = decode4to3(src, dest);
+        if (ret < 0) {
+            return ret;
+        }
+        src += 4;
+        dest += 3;
+        srclen -= 4;
+    }
+
+    switch (srclen) {
+    case 3:
+        return decode3to2(src, dest);
+    case 2:
+        return decode2to1(src, dest);
+    case 1:
+        return -1;
+    default: /* 0 */
+        return 0;
+    }
+}
diff --git a/base64.h b/base64.h
new file mode 100644
index 0000000..07e72a8
--- /dev/null
+++ b/base64.h
@@ -0,0 +1,19 @@ 
+/*
+ * Base64 encoder/decoder conforming to RFC 4648
+ * (based on Mozilla's nsprpub/lib/libc/src/base64.c)
+ *
+ * Copyright (C) 2010 Siemens AG
+ *
+ * Authors:
+ *  Jan Kiszka <jan.kiszka@siemens.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#include <inttypes.h>
+#include <stddef.h>
+
+void base64_encode(const uint8_t *src, size_t srclen, char *dest);
+int base64_decode(const char *src, size_t srclen, uint8_t *dest);