107 lines
2.9 KiB
C++
107 lines
2.9 KiB
C++
#include <euler/stream.hpp>
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#include <algorithm>
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#include <cstring>
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namespace euler {
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file_stream::file_stream(
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syscall::stream_handle handle, bool may_read,
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uint64_t length, uint64_t position)
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: handle(handle), may_read(may_read), buffer_loaded(false),
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length(length), position(position) {}
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syscall::stream_result file_stream::seek(
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syscall::seek_from from, int64_t offset) {
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int64_t new_position = offset +
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(from == syscall::seek_from::beginning ? 0 :
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from == syscall::seek_from::end ? length : position);
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if (new_position < 0 || (uint64_t)new_position > length)
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return syscall::stream_result::out_of_bounds;
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position = new_position;
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return syscall::stream_result::success;
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}
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std::pair<uint64_t, syscall::stream_result>
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file_stream::read(uint64_t bytes, void *into) {
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if (!may_read)
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return {0, syscall::stream_result::not_readable};
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uint64_t have_read = 0;
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syscall::stream_result result = syscall::stream_result::success;
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uint64_t end = position + bytes;
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if (end > length) {
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end = length;
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result = syscall::stream_result::out_of_bounds;
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}
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uint64_t block_start = (position / 1024) * 1024;
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while (position < end) {
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uint64_t length_in_this_block =
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std::min(end, block_start + 1024) - position;
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if (buffer_loaded && buffer_start == block_start)
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memcpy(into, buffer + position - block_start, length_in_this_block);
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else if (length_in_this_block == 1024) {
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syscall::stream_result seek_result =
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syscall::seek_stream(
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handle, syscall::seek_from::beginning, block_start);
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if (seek_result != syscall::stream_result::success)
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return {have_read, seek_result};
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syscall::stream_result read_result =
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syscall::read_from_stream(handle, 1024, into);
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if (read_result != syscall::stream_result::success)
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return {have_read, read_result};
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}
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else {
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syscall::stream_result seek_result =
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syscall::seek_stream(
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handle, syscall::seek_from::beginning, block_start);
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if (seek_result != syscall::stream_result::success)
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return {have_read, seek_result};
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uint64_t buffer_length = std::min(1024UL, length - block_start);
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syscall::stream_result read_result =
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syscall::read_from_stream(handle, buffer_length, buffer);
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if (read_result != syscall::stream_result::success) {
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buffer_loaded = false;
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return {have_read, read_result};
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}
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buffer_loaded = true;
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buffer_start = block_start;
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memcpy(into, buffer + position - block_start, length_in_this_block);
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}
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into = (uint8_t *)into + length_in_this_block;
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have_read += length_in_this_block;
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position += length_in_this_block;
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block_start += 1024;
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}
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return {have_read, result};
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}
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void file_stream::close() {
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syscall::close_stream(handle);
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}
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}
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