102 lines
2.4 KiB
C++
102 lines
2.4 KiB
C++
#include <euler/syscall.hpp>
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#include <cassert>
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#include <cstring>
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#include <cstdio>
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namespace euler {
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//read-only with no error bits for now
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struct file_t {
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syscall::file_handle handle;
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//TODO: variable size buffer? maybe a multiple of block size for device?
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char buffer[1024];
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//in bytes, aligned to buffer size; 1 for no buffer loaded
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uint64_t buffer_start;
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bool is_offset_in_buffer() {
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return
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buffer_start != 1 && offset >= buffer_start &&
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offset < buffer_start + 1024;
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}
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syscall::file_result ensure_offset_in_buffer() {
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if (is_offset_in_buffer())
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return syscall::file_result::success;
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uint64_t new_buffer_start = (offset / 1024) * 1024;
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uint64_t new_buffer_end = new_buffer_start + 1024;
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if (length < new_buffer_end)
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new_buffer_end = length;
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syscall::file_result result = _syscall_read_from_file(
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handle, new_buffer_start, new_buffer_end - new_buffer_start, buffer);
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if (result == syscall::file_result::success)
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buffer_start = new_buffer_start;
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return result;
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}
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uint64_t offset;
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uint64_t length;
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};
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}
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namespace std {
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FILE *fopen(const char *path, const char *mode) {
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assert(mode[0] == 'r' && mode[1] == '\0');
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euler::syscall::file_handle handle;
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euler::syscall::file_result result =
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_syscall_open_file(path, strlen(path), handle);
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if (result != euler::syscall::file_result::success)
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return 0;
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uint64_t length;
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result = _syscall_get_file_length(handle, length);
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if (result != euler::syscall::file_result::success) {
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_syscall_close_file(handle);
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return 0;
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}
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return new FILE {
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.handle = handle,
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.buffer = {},
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.buffer_start = 1,
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.offset = 0,
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.length = length
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};
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}
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int fclose(FILE *file) {
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_syscall_close_file(file->handle);
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delete file;
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return 0;
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}
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int fgetc(FILE *from) {
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if (from->offset >= from->length)
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return EOF;
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assert(
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from->ensure_offset_in_buffer() == euler::syscall::file_result::success);
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char ch = from->buffer[from->offset - from->buffer_start];
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++from->offset;
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return ch;
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}
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int ungetc(int ch, FILE *from) {
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if (ch == EOF || from->offset == 0)
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return EOF;
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--from->offset;
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if (!from->is_offset_in_buffer()) {
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++from->offset;
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return EOF;
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}
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from->buffer[from->offset - from->buffer_start] = ch;
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return ch;
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}
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}
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