postgis/liblwgeom/bytebuffer.c

/**********************************************************************
 *
 * PostGIS - Spatial Types for PostgreSQL
 * http://postgis.net
 *
 * PostGIS is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * PostGIS is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with PostGIS.  If not, see <http://www.gnu.org/licenses/>.
 *
 **********************************************************************
 *
 * Copyright 2015 Nicklas Avén <nicklas.aven@jordogskog.no>
 *
 **********************************************************************/



#include "liblwgeom_internal.h"
#include "bytebuffer.h"


/**
* Allocate just the internal buffer of an existing bytebuffer_t
* struct. Useful for allocating short-lived bytebuffers off the stack.
*/
void
bytebuffer_init_with_size(bytebuffer_t *s, size_t size)
{
	if ( size < BYTEBUFFER_STATICSIZE )
	{
		s->capacity = BYTEBUFFER_STATICSIZE;
		s->buf_start = s->buf_static;
	}
	else
	{
		s->buf_start = lwalloc(size);
		s->capacity = size;
	}
	s->readcursor = s->writecursor = s->buf_start;
	memset(s->buf_start, 0, s->capacity);
}

/**
* Free the bytebuffer_t and all memory managed within it.
*/
void
bytebuffer_destroy_buffer(bytebuffer_t *s)
{
	if ( s->buf_start != s->buf_static )
	{
		lwfree(s->buf_start);
		s->buf_start = NULL;
	}

	return;
}

/**
* If necessary, expand the bytebuffer_t internal buffer to accomodate the
* specified additional size.
*/
static inline void
bytebuffer_makeroom(bytebuffer_t *s, size_t size_to_add)
{
	LWDEBUGF(2,"Entered bytebuffer_makeroom with space need of %d", size_to_add);
	size_t current_write_size = (s->writecursor - s->buf_start);
	size_t capacity = s->capacity;
	size_t required_size = current_write_size + size_to_add;

	LWDEBUGF(2,"capacity = %d and required size = %d",capacity ,required_size);
	while (capacity < required_size)
		capacity *= 2;

	if ( capacity > s->capacity )
	{
		size_t current_read_size = (s->readcursor - s->buf_start);
		LWDEBUGF(4,"We need to realloc more memory. New capacity is %d", capacity);
		if ( s->buf_start == s->buf_static )
		{
			s->buf_start = lwalloc(capacity);
			memcpy(s->buf_start, s->buf_static, s->capacity);
		}
		else
		{
			s->buf_start = lwrealloc(s->buf_start, capacity);
		}
		s->capacity = capacity;
		s->writecursor = s->buf_start + current_write_size;
		s->readcursor = s->buf_start + current_read_size;
	}
	return;
}

/** Returns a copy of the internal buffer */
lwvarlena_t *
bytebuffer_get_buffer_varlena(const bytebuffer_t *s)
{
	size_t bufsz = bytebuffer_getlength(s);
	lwvarlena_t *v = lwalloc(bufsz + LWVARHDRSZ);
	memcpy(v->data, s->buf_start, bufsz);
	LWSIZE_SET(v->size, bufsz + LWVARHDRSZ);
	return v;
}

/** Returns a read-only reference to the internal buffer */
const uint8_t*
bytebuffer_get_buffer(const bytebuffer_t *s, size_t *buffer_length)
{
	if ( buffer_length )
		*buffer_length = bytebuffer_getlength(s);
	return s->buf_start;
}

/**
* Writes a uint8_t value to the buffer
*/
void
bytebuffer_append_byte(bytebuffer_t *s, const uint8_t val)
{
	LWDEBUGF(2,"Entered bytebuffer_append_byte with value %d", val);
	bytebuffer_makeroom(s, 1);
	*(s->writecursor)=val;
	s->writecursor += 1;
	return;
}

/**
* Writes a uint8_t value to the buffer
*/
void
bytebuffer_append_bytebuffer(bytebuffer_t *write_to,bytebuffer_t *write_from )
{
	LWDEBUG(2,"bytebuffer_append_bytebuffer");
	size_t size = bytebuffer_getlength(write_from);
	bytebuffer_makeroom(write_to, size);
	memcpy(write_to->writecursor, write_from->buf_start, size);
	write_to->writecursor += size;
	return;
}

/**
* Writes a signed varInt to the buffer
*/
void
bytebuffer_append_varint(bytebuffer_t *b, const int64_t val)
{
	bytebuffer_makeroom(b, 16);
	b->writecursor += varint_s64_encode_buf(val, b->writecursor);
	return;
}

/**
* Writes a unsigned varInt to the buffer
*/
void
bytebuffer_append_uvarint(bytebuffer_t *b, const uint64_t val)
{
	bytebuffer_makeroom(b, 16);
	b->writecursor += varint_u64_encode_buf(val, b->writecursor);
	return;
}

/**
 * Returns the length of the current buffer
 */
size_t
bytebuffer_getlength(const bytebuffer_t *s)
{
	return (size_t)(s->writecursor - s->buf_start);
}

/* Unused functions */
#if 0

/** Returns a copy of the internal buffer */
uint8_t*
bytebuffer_get_buffer_copy(const bytebuffer_t *s, size_t *buffer_length)
{
	size_t bufsz = bytebuffer_getlength(s);
	uint8_t *buf = lwalloc(bufsz);
	memcpy(buf, s->buf_start, bufsz);
	if ( buffer_length )
		*buffer_length = bufsz;
	return buf;
}

/**
* Allocate a new bytebuffer_t. Use bytebuffer_destroy to free.
*/
bytebuffer_t*
bytebuffer_create(void)
{
	LWDEBUG(2,"Entered bytebuffer_create");
	return bytebuffer_create_with_size(BYTEBUFFER_STARTSIZE);
}

 /**
* Allocate a new bytebuffer_t. Use bytebuffer_destroy to free.
*/
bytebuffer_t*
bytebuffer_create_with_size(size_t size)
{
	LWDEBUGF(2,"Entered bytebuffer_create_with_size %d", size);
	bytebuffer_t *s;

	s = lwalloc(sizeof(bytebuffer_t));
	if ( size < BYTEBUFFER_STATICSIZE )
	{
		s->capacity = BYTEBUFFER_STATICSIZE;
		s->buf_start = s->buf_static;
	}
	else
	{
		s->buf_start = lwalloc(size);
		s->capacity = size;
	}
	s->readcursor = s->writecursor = s->buf_start;
	memset(s->buf_start,0,s->capacity);
	LWDEBUGF(4,"We create a buffer on %p of %d bytes", s->buf_start, s->capacity);
	return s;
}

/**
* Free the bytebuffer_t and all memory managed within it.
*/
void
bytebuffer_destroy(bytebuffer_t *s)
{
	bytebuffer_destroy_buffer(s);
	if ( s )
		lwfree(s);

	return;
}

/**
* Set the read cursor to the beginning
*/
void
bytebuffer_reset_reading(bytebuffer_t *s)
{
	s->readcursor = s->buf_start;
}

 /**
* Reset the bytebuffer_t. Useful for starting a fresh string
* without the expense of freeing and re-allocating a new
* bytebuffer_t.
*/
void
bytebuffer_clear(bytebuffer_t *s)
{
	s->readcursor = s->writecursor = s->buf_start;
}

/**
* Writes a uint8_t value to the buffer
*/
void
bytebuffer_append_bulk(bytebuffer_t *s, void * start, size_t size)
{
	LWDEBUGF(2,"bytebuffer_append_bulk with size %d",size);
	bytebuffer_makeroom(s, size);
	memcpy(s->writecursor, start, size);
	s->writecursor += size;
	return;
}

/*
* Writes Integer to the buffer
*/
void
bytebuffer_append_int(bytebuffer_t *buf, const int val, int swap)
{
	LWDEBUGF(2,"Entered bytebuffer_append_int with value %d, swap = %d", val, swap);

	LWDEBUGF(4,"buf_start = %p and write_cursor=%p", buf->buf_start,buf->writecursor);
	char *iptr = (char*)(&val);
	int i = 0;

	if ( sizeof(int) != WKB_INT_SIZE )
	{
		lwerror("Machine int size is not %d bytes!", WKB_INT_SIZE);
	}

	bytebuffer_makeroom(buf, WKB_INT_SIZE);
	/* Machine/request arch mismatch, so flip byte order */
	if ( swap)
	{
		LWDEBUG(4,"Ok, let's do the swaping thing");
		for ( i = 0; i < WKB_INT_SIZE; i++ )
		{
			*(buf->writecursor) = iptr[WKB_INT_SIZE - 1 - i];
			buf->writecursor += 1;
		}
	}
	/* If machine arch and requested arch match, don't flip byte order */
	else
	{
		LWDEBUG(4,"Ok, let's do the memcopying thing");
		memcpy(buf->writecursor, iptr, WKB_INT_SIZE);
		buf->writecursor += WKB_INT_SIZE;
	}

	LWDEBUGF(4,"buf_start = %p and write_cursor=%p", buf->buf_start,buf->writecursor);
	return;

 }





 /**
* Writes a float64 to the buffer
*/
void
bytebuffer_append_double(bytebuffer_t *buf, const double val, int swap)
{
	LWDEBUGF(2,"Entered bytebuffer_append_double with value %lf swap = %d", val, swap);

	LWDEBUGF(4,"buf_start = %p and write_cursor=%p", buf->buf_start,buf->writecursor);
	char *dptr = (char*)(&val);
	int i = 0;

	if ( sizeof(double) != WKB_DOUBLE_SIZE )
	{
		lwerror("Machine double size is not %d bytes!", WKB_DOUBLE_SIZE);
	}

	bytebuffer_makeroom(buf, WKB_DOUBLE_SIZE);

	/* Machine/request arch mismatch, so flip byte order */
	if ( swap )
	{
		LWDEBUG(4,"Ok, let's do the swapping thing");
		for ( i = 0; i < WKB_DOUBLE_SIZE; i++ )
		{
			*(buf->writecursor) = dptr[WKB_DOUBLE_SIZE - 1 - i];
			buf->writecursor += 1;
		}
	}
	/* If machine arch and requested arch match, don't flip byte order */
	else
	{
		LWDEBUG(4,"Ok, let's do the memcopying thing");
		memcpy(buf->writecursor, dptr, WKB_DOUBLE_SIZE);
		buf->writecursor += WKB_DOUBLE_SIZE;
	}

	LWDEBUG(4,"Return from bytebuffer_append_double");
	return;

 }

 /**
* Reads a signed varInt from the buffer
*/
int64_t
bytebuffer_read_varint(bytebuffer_t *b)
{
	size_t size;
	int64_t val = varint_s64_decode(b->readcursor, b->buf_start + b->capacity, &size);
	b->readcursor += size;
	return val;
}

 /**
* Reads a unsigned varInt from the buffer
*/
uint64_t
bytebuffer_read_uvarint(bytebuffer_t *b)
{
	size_t size;
	uint64_t val = varint_u64_decode(b->readcursor, b->buf_start + b->capacity, &size);
	b->readcursor += size;
	return val;
}


 /**
* Returns a new bytebuffer were both ingoing bytebuffers is merged.
* Caller is responsible for freeing both incoming bytebuffers and resulting bytebuffer
*/
bytebuffer_t*
bytebuffer_merge(bytebuffer_t **buff_array, int nbuffers)
{
	size_t total_size = 0, current_size, acc_size = 0;
	int i;
	for ( i = 0; i < nbuffers; i++ )
	{
		total_size += bytebuffer_getlength(buff_array[i]);
	}

	bytebuffer_t *res = bytebuffer_create_with_size(total_size);
	for ( i = 0; i < nbuffers; i++)
	{
		current_size = bytebuffer_getlength(buff_array[i]);
		memcpy(res->buf_start+acc_size, buff_array[i]->buf_start, current_size);
		acc_size += current_size;
	}
	res->writecursor = res->buf_start + total_size;
	res->readcursor = res->buf_start;
	return res;
}

#endif