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/*
* Minimal bootstrap RTL (runtime library) - Reader (input) functions.
*
* Copyright © 2026 Samuel Lidén Borell <samuel@kodafritt.se>
*
* SPDX-License-Identifier: EUPL-1.2+ OR LGPL-2.1-or-later
*/
#include <assert.h>
#include <string.h>
#include "rtl.h"
#include "internal.h"
#define DEFAULT_BUFFERSIZE 128
/**< Maximum of "non-unsigned" (31 bit range) integer. */
#define PLAIN_SLULINT_MAX 0x7FFFFFFF
#define NO_LIMIT SLUL_INT_MAX
struct Reader {
FILE *file;
/**
* Filename for use in error messages.
* Note that the filename should NOT be exposed to the application.
*/
const char *filename;
SlulInt limit_left;
SlulInt lookahead_size;
unsigned char *lookahead_buffer;
unsigned char *lookahead;
};
struct Reader *Reader__from_file(FILE *f, const char *filename)
{
struct Reader *rd = malloc(sizeof(struct Reader));
OOM_CHECK(rd);
assert(f != NULL);
assert(filename != NULL);
rd->file = f;
rd->filename = filename;
rd->limit_left = NO_LIMIT;
rd->lookahead_size = 0;
rd->lookahead_buffer = NULL;
return rd;
}
struct Reader *Reader__from_filename(const char *filename)
{
FILE *f;
f = fopen(filename, "rb");
if (!f) {
perror(filename);
exit(EXIT_FAILURE);
}
return Reader__from_file(f, filename);
}
static SLUL_NORETURN void file_perror(struct Reader *rd)
{
perror(rd->filename);
exit(EXIT_FAILURE);
}
static SLUL_NORETURN void file_error(struct Reader *rd, const char *errmsg)
{
fprintf(stderr, "error: %s: %s\n", rd->filename, errmsg);
exit(EXIT_FAILURE);
}
static int readbyte(struct Reader *rd)
{
assert(rd != NULL);
if (rd->limit_left != NO_LIMIT) {
if (rd->limit_left-- == 0) {
file_error(rd, "Exceeded size limit");
}
}
if (rd->lookahead_size) {
int byte = *(rd->lookahead++);
if (--rd->lookahead_size == 0) {
free(rd->lookahead_buffer);
}
return byte;
} else {
return getc(rd->file);
}
}
static SlulInt readbytes(struct Reader *rd, SlulInt size, unsigned char *out)
{
SlulInt ls;
SlulInt numread = 0;
SlulInt maxread = size;
assert(rd != NULL);
assert(size <= PLAIN_SLULINT_MAX);
assert(out != NULL);
if (size == 0) {
return 0;
}
/* Handle remaining limit, if a limit has been set */
{
SlulInt limit = rd->limit_left;
if (limit != NO_LIMIT) {
if (size > limit) {
size = limit+1;
maxread = limit;
limit = 0;
} else {
limit -= size;
}
rd->limit_left = limit;
}
}
/* Read from lookahead buffer, if lookahead was done before */
ls = rd->lookahead_size;
if (ls) {
ls = (ls <= size ? ls : size);
memcpy(out, rd->lookahead, (size_t)ls);
rd->lookahead += ls;
if ((rd->lookahead_size -= ls) == 0) {
free(rd->lookahead_buffer);
rd->lookahead_buffer = NULL;
}
out += ls;
size -= ls;
numread += ls;
}
/* Read from underlying file (unless satisfied by lookahead buffer) */
if (size) {
numread += (SlulInt)fread(out, 1, (size_t)size, rd->file);
}
if (numread > maxread) {
file_error(rd, "Exceeded size limit");
}
return numread;
}
static SLUL_NORETURN void handle_eof(struct Reader *rd)
{
if (ferror(rd->file)) {
file_perror(rd);
} else {
file_error(rd, "Unexpected end of file");
}
}
static void try_read(struct Reader *rd, SlulInt len, unsigned char *buffer)
{
if (readbytes(rd, len, buffer) != len) {
handle_eof(rd);
}
}
SlulInt Reader_read_u8(struct Reader *rd)
{
int byte = readbyte(rd);
if (byte == EOF) {
handle_eof(rd);
}
assert(byte >= 0);
return (SlulInt)byte;
}
SlulInt Reader_read_u16_le(struct Reader *rd)
{
unsigned char bytes[2];
try_read(rd, 2, bytes);
return (bytes[0] & 0xFFU) |
((bytes[1] & 0xFFU) << 8U);
}
SlulInt Reader_read_u32_le(struct Reader *rd)
{
unsigned char bytes[4];
try_read(rd, 4, bytes);
return (bytes[0] & 0xFFU) |
((bytes[1] & 0xFFU) << 8U) |
((bytes[2] & 0xFFU) << 16U) |
((bytes[3] & 0xFFU) << 24U);
}
void Reader_expect(struct Reader *rd, const String *s)
{
const unsigned char *sp;
SlulInt len;
assert(s != NULL);
sp = SLUL__decode_string(s, &len);
while (len--) {
if (Reader_read_u8(rd) != *(sp++)) {
file_error(rd, "Input does not contain expected string");
}
}
}
void Reader_expect_repeated(struct Reader *rd,
const String *s,
SlulInt repeat_count)
{
SlulInt i;
assert(s != NULL);
for (i = repeat_count; i != 0; i--) {
Reader_expect(rd, s);
}
}
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