#include "firebird.h"

#include "../common/classes/ClumpletReader.h"
#include "fb_exception.h"

namespace Firebird {

void ClumpletReader::read_past_eof() {
	fatal_exception::raise("Reading past the end of clumplet buffer");
}

void ClumpletReader::invalid_structure() {
	fatal_exception::raise("Invalid clumplet buffer structure");
}

UCHAR ClumpletReader::getBufferTag() {
	UCHAR* buffer_end = getBufferEnd();
	UCHAR* buffer_start = getBuffer();
	if (buffer_end - buffer_start == 0) {
		invalid_structure();
		return 0;
	}
	return buffer_start[0];
}

void ClumpletReader::moveNext() {
	UCHAR* clumplet = getBuffer() + cur_offset;
	UCHAR* buffer_end = getBufferEnd();

	// Check for EOF
	if (clumplet >= buffer_end) {
		read_past_eof();
		return;
	}

	// It appears we didn't receive length component for clumplet
	if (buffer_end - clumplet < 2) {
		invalid_structure();
		return;
	}

	size_t length = clumplet[1];
	cur_offset += length + 1;
}

// Methods which work with currently selected clumplet
UCHAR ClumpletReader::getClumpTag() {
	UCHAR* clumplet = getBuffer() + cur_offset;
	UCHAR* buffer_end = getBufferEnd();

	// Check for EOF
	if (clumplet >= buffer_end) {
		read_past_eof();
		return 0;
	}

	return clumplet[0];
}

size_t ClumpletReader::getClumpLength() {
	UCHAR* clumplet = getBuffer() + cur_offset;
	UCHAR* buffer_end = getBufferEnd();

	// Check for EOF
	if (clumplet >= buffer_end) {
		read_past_eof();
		return 0;
	}

	// See if we have length byte available
	if (buffer_end - clumplet < 2) {
		invalid_structure();
		return 0;
	}

	// See if length seems kosher
	size_t length = clumplet[1];
	if (buffer_end - clumplet < length + 1) {
		invalid_structure();
		return buffer_end - clumplet - 1;
	}

	return length;
}

SLONG ClumpletReader::getInt() {
	UCHAR* clumplet = getBuffer() + cur_offset;
	size_t length = getClumpLength();

	if (length > 4)
		invalid_structure();

	UCHAR* ptr = clumplet + 2;

	// This code is taken from gds__vax_integer
	SLONG value = 0;
	int shift = 0;
	while (--length >= 0) {
		value += ((SLONG) *ptr++) << shift;
		shift += 8;
	}

	return value;
}

SINT64 ClumpletReader::getBigInt() {
	UCHAR* clumplet = getBuffer() + cur_offset;
	size_t length = getClumpLength();

	if (length > 8)
		invalid_structure();

	UCHAR* ptr = clumplet + 2;

	// This code is taken from isc_portable_integer
	SINT64 value = 0;
	int shift = 0;
	while (--length >= 0) {
		value += ((SINT64) *ptr++) << shift;
		shift += 8;
	}

	return value;
}

string& ClumpletReader::getString(string& str) {
	UCHAR* clumplet = getBuffer() + cur_offset;
	size_t length = getClumpLength();
	str.assign(reinterpret_cast<char*>(clumplet + 2), length);
	return str;
}


}