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Buffer: graciously handle padding in base64-encoded input.
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@bnoordhuis @ry
bnoordhuis authored and ry committed Jul 30, 2010
1 parent cf49fc7 commit f72ac17
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Showing 2 changed files with 53 additions and 79 deletions.
124 changes: 45 additions & 79 deletions src/node_buffer.cc
View file
Expand Up @@ -86,6 +86,30 @@ static inline void blob_unref(Blob *blob) {
}
}

static inline size_t base64_decoded_size(const char *src, size_t size) {
const char *const end = src + size;
const int remainder = size % 4;

size = (size / 4) * 3;
if (remainder) {
if (size == 0 && remainder == 1) {
// special case: 1-byte input cannot be decoded
size = 0;
} else {
// non-padded input, add 1 or 2 extra bytes
size += 1 + (remainder == 3);
}
}

// check for trailing padding (1 or 2 bytes)
if (size > 0) {
if (end[-1] == '=') size--;
if (end[-2] == '=') size--;
}

return size;
}

#if 0
// When someone calls buffer.asciiSlice, data is not copied. Instead V8
// references in the underlying Blob with this ExternalAsciiStringResource.
Expand Down Expand Up @@ -151,25 +175,9 @@ Handle<Value> Buffer::New(const Arguments &args) {
int length = e == UTF8 ? s->Utf8Length() : s->Length();

// input gets base64-decoded, adjust buffer size
if (e == BASE64 && length > 0) {
const int remainder = length % 4;

length = (length / 4) * 3;
if (remainder) {
if (length == 0 && remainder == 1) {
// special case: 1-byte input cannot be decoded, return empty buffer
length = 0;
} else {
// non-padded input, add 1 or 2 extra bytes
length += 1 + (remainder == 3);
}
} else {
// check for trailing padding (1 or 2 bytes)
const String::AsciiValue data(s);
const char *const end = *data + data.length();
if (end[-1] == '=') length--;
if (end[-2] == '=') length--;
}
if (e == BASE64) {
const String::AsciiValue data(s);
length = base64_decoded_size(*data, data.length());
}

buffer = new Buffer(length);
Expand Down Expand Up @@ -517,7 +525,6 @@ Handle<Value> Buffer::AsciiWrite(const Arguments &args) {
return scope.Close(Integer::New(written));
}


// var bytesWritten = buffer.base64Write(string, offset);
Handle<Value> Buffer::Base64Write(const Arguments &args) {
HandleScope scope;
Expand Down Expand Up @@ -549,68 +556,27 @@ Handle<Value> Buffer::Base64Write(const Arguments &args) {
"Offset is out of bounds")));
}

char *input = *s;
int input_len = s.length();

char *start = buffer->data() + offset;
char *p = start;
const char *pe = buffer->data() + buffer->length_;

int i = 0;
char a,b,c,d, last;

bool b_oob, c_oob;

while (i < input_len && p < pe) {
last = input[i];
if (last == '=' || i >= input_len) break;
a = unbase64_table[last];
i++;

last = input[i];
if (last == '=' || i >= input_len) {
b = 0;
b_oob = true;
} else {
b = unbase64_table[last];
b_oob = false;
}
i++;

last = input[i];
if (b_oob || last == '=' || i >= input_len) {
c = 0;
c_oob = true;
} else {
c = unbase64_table[last];
c_oob = false;
}
i++;

last = input[i];
if (c_oob || last == '=' || i >= input_len) {
d = 0;
} else {
d = unbase64_table[last];
}
i++;

*p = (a << 2) | ((b & 0x30) >> 4);
if (last == '=' && *p == '\0') break;
if (++p == pe) break;

if (b_oob) break;
*p = ((b & 0x0F) << 4) | ((c & 0x3c) >> 2);
if (last == '=' && *p == '\0') break;
if (++p == pe) break;
const size_t size = base64_decoded_size(*s, s.length());
if (size > buffer->length_ - offset) {
// throw exception, don't silently truncate
return ThrowException(Exception::TypeError(String::New(
"Buffer too small")));
}

if (c_oob) break;
*p = ((c & 0x03) << 6) | (d & 0x3f);
if (last == '=' && *p == '\0') break;
if (++p == pe) break;
char a, b, c, d;
char *dst = buffer->data();
const char *src = *s;
const char *const srcEnd = src + s.length();

while (src < srcEnd) {
const int remaining = srcEnd - src;
if (remaining == 0 || *src == '=') break; a = unbase64_table[*src++];
if (remaining == 1 || *src == '=') break; b = unbase64_table[*src++]; *dst++ = (a << 2) | ((b & 0x30) >> 4);
if (remaining == 2 || *src == '=') break; c = unbase64_table[*src++]; *dst++ = ((b & 0x0F) << 4) | ((c & 0x3C) >> 2);
if (remaining == 3 || *src == '=') break; d = unbase64_table[*src++]; *dst++ = ((c & 0x03) << 6) | (d & 0x3F);
}

return scope.Close(Integer::New(p - start));
return scope.Close(Integer::New(size));
}


Expand Down
8 changes: 8 additions & 0 deletions test/simple/test-buffer.js
View file
Expand Up @@ -298,3 +298,11 @@ assert.equal(new Buffer('KioqKioqKioqKioqKioqKg', 'base64').toString(), '*******
assert.equal(new Buffer('KioqKioqKioqKioqKioqKio', 'base64').toString(), '*****************');
assert.equal(new Buffer('KioqKioqKioqKioqKioqKioqKg', 'base64').toString(), '*******************');
assert.equal(new Buffer('KioqKioqKioqKioqKioqKioqKio', 'base64').toString(), '********************');

// handle padding graciously, multiple-of-4 or not
assert.equal(new Buffer('72INjkR5fchcxk9+VgdGPFJDxUBFR5/rMFsghgxADiw==', 'base64').length, 32);
assert.equal(new Buffer('72INjkR5fchcxk9+VgdGPFJDxUBFR5/rMFsghgxADiw=', 'base64').length, 32);
assert.equal(new Buffer('72INjkR5fchcxk9+VgdGPFJDxUBFR5/rMFsghgxADiw', 'base64').length, 32);
assert.equal(new Buffer('w69jACy6BgZmaFvv96HG6MYksWytuZu3T1FvGnulPg==', 'base64').length, 31);
assert.equal(new Buffer('w69jACy6BgZmaFvv96HG6MYksWytuZu3T1FvGnulPg=', 'base64').length, 31);
assert.equal(new Buffer('w69jACy6BgZmaFvv96HG6MYksWytuZu3T1FvGnulPg', 'base64').length, 31);

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