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read_chunk.hpp
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read_chunk.hpp
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#pragma once
#include <iostream>
#include <vector>
#include <stdexcept>
#include <cassert>
template< typename T >
void read_chunk(std::istream &from, std::string const &magic, std::vector< T > *_to) {
assert(_to);
auto &to = *_to;
struct ChunkHeader {
char magic[4] = {'\0', '\0', '\0', '\0'};
uint32_t size = 0;
};
static_assert(sizeof(ChunkHeader) == 8, "header is packed");
ChunkHeader header;
if (!from.read(reinterpret_cast< char * >(&header), sizeof(header))) {
throw std::runtime_error("Failed to read chunk header");
}
if (std::string(header.magic,4) != magic) {
throw std::runtime_error("Unexpected magic number in chunk");
}
if (header.size % sizeof(T) != 0) {
throw std::runtime_error("Size of chunk not divisible by element size");
}
to.resize(header.size / sizeof(T));
if (!from.read(reinterpret_cast< char * >(&to[0]), to.size() * sizeof(T))) {
throw std::runtime_error("Failed to read chunk data.");
}
}