blob: 0b38f87381a8fc246c97221e7a9bddf08fb82405 [file] [log] [blame]
/**
* @author: Jeff Thompson
* Derived from BinaryXMLEncoder.js by Meki Cheraoui.
* See COPYING for copyright and distribution information.
*/
#include <math.h>
#include "../util/ndn_memory.h"
#include "BinaryXML.h"
#include "BinaryXMLEncoder.h"
enum {
ENCODING_LIMIT_1_BYTE = ((1 << ndn_BinaryXml_TT_VALUE_BITS) - 1),
ENCODING_LIMIT_2_BYTES = ((1 << (ndn_BinaryXml_TT_VALUE_BITS + ndn_BinaryXml_REGULAR_VALUE_BITS)) - 1),
ENCODING_LIMIT_3_BYTES = ((1 << (ndn_BinaryXml_TT_VALUE_BITS + 2 * ndn_BinaryXml_REGULAR_VALUE_BITS)) - 1)
};
/**
* Call ndn_DynamicUCharArray_ensureLength to ensure that there is enough room in the output, and copy
* array to the output. This does not write a header.
* @param self pointer to the ndn_BinaryXmlEncoder struct
* @param array the array to copy
* @param arrayLength the length of the array
* @return 0 for success, else an error code
*/
static ndn_Error writeArray(struct ndn_BinaryXmlEncoder *self, unsigned char *array, unsigned int arrayLength)
{
ndn_Error error;
if (error = ndn_DynamicUCharArray_ensureLength(&self->output, self->offset + arrayLength))
return error;
ndn_memcpy(self->output.array + self->offset, array, arrayLength);
self->offset += arrayLength;
return 0;
}
/**
* Return the number of bytes to encode a header of value x.
*/
static unsigned int getNHeaderEncodingBytes(unsigned int x)
{
// Do a quick check for pre-compiled results.
if (x <= ENCODING_LIMIT_1_BYTE)
return 1;
if (x <= ENCODING_LIMIT_2_BYTES)
return 2;
if (x <= ENCODING_LIMIT_3_BYTES)
return 3;
unsigned int nBytes = 1;
// Last byte gives you TT_VALUE_BITS.
// Remainder each gives you REGULAR_VALUE_BITS.
x >>= ndn_BinaryXml_TT_VALUE_BITS;
while (x != 0) {
++nBytes;
x >>= ndn_BinaryXml_REGULAR_VALUE_BITS;
}
return nBytes;
}
/**
* Reverse the length bytes in array.
* @param array
* @param length
*/
static void reverse(unsigned char *array, unsigned int length)
{
if (length == 0)
return;
unsigned char *left = array;
unsigned char *right = array + length - 1;
while (left < right) {
// Swap.
unsigned char temp = *left;
*left = *right;
*right = temp;
++left;
--right;
}
}
/**
* Write x as an unsigned decimal integer to the output with the digits in reverse order, using ndn_DynamicUCharArray_ensureLength.
* This does not write a header.
* We encode in reverse order, because this is the natural way to encode the digits, and the caller can reverse as needed.
* @param self pointer to the ndn_BinaryXmlEncoder struct
* @param x the unsigned int to write
* @return 0 for success, else an error code
*/
static ndn_Error encodeReversedUnsignedDecimalInt(struct ndn_BinaryXmlEncoder *self, unsigned int x)
{
while (1) {
ndn_Error error;
if (error = ndn_DynamicUCharArray_ensureLength(&self->output, self->offset + 1))
return error;
self->output.array[self->offset++] = (unsigned char)(x % 10 + '0');
x /= 10;
if (x == 0)
break;
}
return 0;
}
/**
* Reverse the buffer in self->output.array, then shift it right by the amount needed to prefix a header with type,
* then encode the header at startOffset.
* startOffser it the position in self-output.array of the first byte of the buffer and self->offset is the first byte past the end.
* We reverse and shift in the same function to avoid unnecessary copying if we first reverse then shift.
* @param self pointer to the ndn_BinaryXmlEncoder struct
* @param startOffset the offset in self->output.array of the start of the buffer to shift right
* @param type the header type
* @return 0 for success, else an error code
*/
static ndn_Error reverseBufferAndInsertHeader
(struct ndn_BinaryXmlEncoder *self, unsigned int startOffset, unsigned int type)
{
unsigned int nBufferBytes = self->offset - startOffset;
unsigned int nHeaderBytes = getNHeaderEncodingBytes(nBufferBytes);
ndn_Error error;
if (error = ndn_DynamicUCharArray_ensureLength(&self->output, self->offset + nHeaderBytes))
return error;
// To reverse and shift at the same time, we first shift nHeaderBytes to the destination while reversing,
// then reverse the remaining bytes in place.
unsigned char *from = self->output.array + startOffset;
unsigned char *fromEnd = from + nHeaderBytes;
unsigned char *to = self->output.array + startOffset + nBufferBytes + nHeaderBytes - 1;
while (from < fromEnd)
*(to--) = *(from++);
// Reverse the remaining bytes in place (if any).
if (nBufferBytes > nHeaderBytes)
reverse(self->output.array + startOffset + nHeaderBytes, nBufferBytes - nHeaderBytes);
// Override the offset to force encodeTypeAndValue to encode at startOffset, then fix the offset.
self->offset = startOffset;
if (error = ndn_BinaryXmlEncoder_encodeTypeAndValue(self, ndn_BinaryXml_UDATA, nBufferBytes))
// We don't really expect to get an error, since we have already ensured the length.
return error;
self->offset = startOffset + nHeaderBytes + nBufferBytes;
return 0;
}
/**
* Split the absolute value of x into 32 bit unsigned integers hi32 and lo32.
* We need this because not all C compilers support 64 bit long long integers, so we carry around
* a high precision value as a double, which we assume has more than 32 bits.
* But we want to do bit-wise operations on integers.
* @param x the double value
* @param hi32 output the high 32 bits
* @param lo32 output the low 32 bits
*/
static inline void splitAbsDouble(double x, unsigned long *hi32, unsigned long *lo32)
{
if (x < 0)
x = -x;
x = round(x);
double twoPower32 = 4294967296.0;
double lo32Double = fmod(x, twoPower32);
*lo32 = (unsigned long)lo32Double;
*hi32 = (unsigned long)((x - lo32Double) / twoPower32);
}
ndn_Error ndn_BinaryXmlEncoder_encodeTypeAndValue(struct ndn_BinaryXmlEncoder *self, unsigned int type, unsigned int value)
{
if (type > ndn_BinaryXml_UDATA)
return NDN_ERROR_header_type_is_out_of_range;
// Encode backwards. Calculate how many bytes we need.
unsigned int nEncodingBytes = getNHeaderEncodingBytes(value);
ndn_Error error;
if (error = ndn_DynamicUCharArray_ensureLength(&self->output, self->offset + nEncodingBytes))
return error;
// Bottom 4 bits of value go in last byte with tag.
self->output.array[self->offset + nEncodingBytes - 1] =
(ndn_BinaryXml_TT_MASK & type |
((ndn_BinaryXml_TT_VALUE_MASK & value) << ndn_BinaryXml_TT_BITS)) |
ndn_BinaryXml_TT_FINAL; // set top bit for last byte
value >>= ndn_BinaryXml_TT_VALUE_BITS;
// Rest of value goes into preceding bytes, 7 bits per byte. (Zero top bit is "more" flag.)
unsigned int i = self->offset + nEncodingBytes - 2;
while (value != 0 && i >= self->offset) {
self->output.array[i] = (value & ndn_BinaryXml_REGULAR_VALUE_MASK);
value >>= ndn_BinaryXml_REGULAR_VALUE_BITS;
--i;
}
if (value != 0)
// This should not happen if getNHeaderEncodingBytes is correct.
return NDN_ERROR_encodeTypeAndValue_miscalculated_N_encoding_bytes;
self->offset+= nEncodingBytes;
return 0;
}
ndn_Error ndn_BinaryXmlEncoder_writeElementClose(struct ndn_BinaryXmlEncoder *self)
{
ndn_Error error;
if (error = ndn_DynamicUCharArray_ensureLength(&self->output, self->offset + 1))
return error;
self->output.array[self->offset] = ndn_BinaryXml_CLOSE;
self->offset += 1;
return 0;
}
ndn_Error ndn_BinaryXmlEncoder_writeBlob(struct ndn_BinaryXmlEncoder *self, unsigned char *value, unsigned int valueLength)
{
ndn_Error error;
if (error = ndn_BinaryXmlEncoder_encodeTypeAndValue(self, ndn_BinaryXml_BLOB, valueLength))
return error;
if (error = writeArray(self, value, valueLength))
return error;
return 0;
}
ndn_Error ndn_BinaryXmlEncoder_writeBlobDTagElement(struct ndn_BinaryXmlEncoder *self, unsigned int tag, unsigned char *value, unsigned int valueLength)
{
ndn_Error error;
if (error = ndn_BinaryXmlEncoder_writeElementStartDTag(self, tag))
return error;
if (error = ndn_BinaryXmlEncoder_writeBlob(self, value, valueLength))
return error;
if (error = ndn_BinaryXmlEncoder_writeElementClose(self))
return error;
return 0;
}
ndn_Error ndn_BinaryXmlEncoder_writeUnsignedDecimalInt(struct ndn_BinaryXmlEncoder *self, unsigned int value)
{
// First write the decimal int (to find out how many bytes it is), then shift it forward to make room for the header.
unsigned int startOffset = self->offset;
ndn_Error error;
if (error = encodeReversedUnsignedDecimalInt(self, value))
return error;
if (error = reverseBufferAndInsertHeader(self, startOffset, ndn_BinaryXml_UDATA))
return error;
return 0;
}
ndn_Error ndn_BinaryXmlEncoder_writeUnsignedDecimalIntDTagElement(struct ndn_BinaryXmlEncoder *self, unsigned int tag, unsigned int value)
{
ndn_Error error;
if (error = ndn_BinaryXmlEncoder_writeElementStartDTag(self, tag))
return error;
if (error = ndn_BinaryXmlEncoder_writeUnsignedDecimalInt(self, value))
return error;
if (error = ndn_BinaryXmlEncoder_writeElementClose(self))
return error;
return 0;
}
ndn_Error ndn_BinaryXmlEncoder_writeAbsDoubleBigEndianBlob(struct ndn_BinaryXmlEncoder *self, double value)
{
unsigned long hi32, lo32;
splitAbsDouble(value, &hi32, &lo32);
// First encode the big endian backwards, then reverseBufferAndInsertHeader will reverse it.
unsigned int startOffset = self->offset;
ndn_Error error;
while (lo32 != 0) {
if (error = ndn_DynamicUCharArray_ensureLength(&self->output, self->offset + 1))
return error;
self->output.array[self->offset++] = (unsigned char)(lo32 & 0xff);
lo32 >>= 8;
}
if (hi32 != 0) {
// Pad the lo values out to 4 bytes.
while (self->offset - startOffset < 4) {
if (error = ndn_DynamicUCharArray_ensureLength(&self->output, self->offset + 1))
return error;
self->output.array[self->offset++] = 0;
}
// Encode hi32
while (hi32 != 0) {
if (error = ndn_DynamicUCharArray_ensureLength(&self->output, self->offset + 1))
return error;
self->output.array[self->offset++] = (unsigned char)(hi32 & 0xff);
hi32 >>= 8;
}
}
if (error = reverseBufferAndInsertHeader(self, startOffset, ndn_BinaryXml_BLOB))
return error;
return 0;
}
ndn_Error ndn_BinaryXmlEncoder_writeTimeMillisecondsDTagElement(struct ndn_BinaryXmlEncoder *self, unsigned int tag, double milliseconds)
{
ndn_Error error;
if (error = ndn_BinaryXmlEncoder_writeElementStartDTag(self, tag))
return error;
if (error = ndn_BinaryXmlEncoder_writeAbsDoubleBigEndianBlob(self, (milliseconds / 1000.0) * 4096.0))
return error;
if (error = ndn_BinaryXmlEncoder_writeElementClose(self))
return error;
return 0;
}