ndn-cpp/c/encoding/BinaryXMLEncoder.c - ndn-cxx - Gitiles

 /**
  * @author: Jeff Thompson
  * Derived from BinaryXMLEncoder.js by Meki Cheraoui.
  * See COPYING for copyright and distribution information.
  */

 #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, using ndn_DynamicUCharArray_ensureLength.
  * This does not write a header.
  * @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 encodeUnsignedDecimalInt(struct ndn_BinaryXMLEncoder *self, unsigned int x)
 {
   // We write the value backwards, then reverse it.
   unsigned int startOffset = self->offset;

   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;
   }

   // Now reverse.
   reverse(self->output.array + startOffset, self->offset - startOffset);
   return 0;
 }

 /**
  * Like memcpy, copy length bytes from source to dest, assuming that the buffers can overlap and that
  * we are shifting the buffer right.
  * Don't use memcpy to shift because its behavior is not guaranteed when the buffers overlap.
  * @param dest
  * @param source
  * @param length
  */
 static void copyBufferRight(unsigned char *dest, unsigned char *source, unsigned int length)
 {
   if (length == 0)
     return;

   // We are shifting right, so start from the end of the buffer.
   unsigned char *from = source + length - 1;
   unsigned char *to = dest + length - 1;
   while (from >= source)
     *(to--) = *(from--);
 }

 /**
  * Shift a buffer in self->output.array right by the amount needed to prefix a header with type, then encode the header
  * at startOffset.
  * The buffer to shift right begins at startOffset and self->offset is at the end.
  * @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 insertHeader
   (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;

   copyBufferRight(self->output.array + startOffset + nHeaderBytes, self->output.array + startOffset, nBufferBytes);

   // 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;
 }

 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 = encodeUnsignedDecimalInt(self, value))
     return error;

   if (error = insertHeader(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_writeUnsignedIntBigEndianBlob(struct ndn_BinaryXMLEncoder *self, unsigned int value)
 {
   // First encode the big endian backwards, then reverse it.
   unsigned int startOffset = self->offset;
   ndn_Error error;
   while (value != 0) {
     if (error = ndn_DynamicUCharArray_ensureLength(&self->output, self->offset + 1))
       return error;

     self->output.array[self->offset++] = (unsigned char)(value & 0xff);
     value >>= 8;
   }

   unsigned int bigEndianLength = self->offset - startOffset;
   reverse(self->output.array + startOffset, bigEndianLength);

   if (error = insertHeader(self, startOffset, ndn_BinaryXML_BLOB))
     return error;

   return 0;
 }
	/**
	* @author: Jeff Thompson
	* Derived from BinaryXMLEncoder.js by Meki Cheraoui.
	* See COPYING for copyright and distribution information.
	*/

	#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, using ndn_DynamicUCharArray_ensureLength.
	* This does not write a header.
	* @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 encodeUnsignedDecimalInt(struct ndn_BinaryXMLEncoder *self, unsigned int x)
	{
	// We write the value backwards, then reverse it.
	unsigned int startOffset = self->offset;

	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;
	}

	// Now reverse.
	reverse(self->output.array + startOffset, self->offset - startOffset);
	return 0;
	}

	/**
	* Like memcpy, copy length bytes from source to dest, assuming that the buffers can overlap and that
	* we are shifting the buffer right.
	* Don't use memcpy to shift because its behavior is not guaranteed when the buffers overlap.
	* @param dest
	* @param source
	* @param length
	*/
	static void copyBufferRight(unsigned char dest, unsigned char source, unsigned int length)
	{
	if (length == 0)
	return;

	// We are shifting right, so start from the end of the buffer.
	unsigned char *from = source + length - 1;
	unsigned char *to = dest + length - 1;
	while (from >= source)
	(to--) = (from--);
	}

	/**
	* Shift a buffer in self->output.array right by the amount needed to prefix a header with type, then encode the header
	* at startOffset.
	* The buffer to shift right begins at startOffset and self->offset is at the end.
	* @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 insertHeader
	(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;

	copyBufferRight(self->output.array + startOffset + nHeaderBytes, self->output.array + startOffset, nBufferBytes);

	// 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;
	}

	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 = encodeUnsignedDecimalInt(self, value))
	return error;

	if (error = insertHeader(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_writeUnsignedIntBigEndianBlob(struct ndn_BinaryXMLEncoder *self, unsigned int value)
	{
	// First encode the big endian backwards, then reverse it.
	unsigned int startOffset = self->offset;
	ndn_Error error;
	while (value != 0) {
	if (error = ndn_DynamicUCharArray_ensureLength(&self->output, self->offset + 1))
	return error;

	self->output.array[self->offset++] = (unsigned char)(value & 0xff);
	value >>= 8;
	}

	unsigned int bigEndianLength = self->offset - startOffset;
	reverse(self->output.array + startOffset, bigEndianLength);

	if (error = insertHeader(self, startOffset, ndn_BinaryXML_BLOB))
	return error;

	return 0;
	}