read.c

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/* ************************************************************************** */
/*      ____    _    _____ ____     _    _   _   _____ _  _   ____  ____      */
/*     / ___|  / \  |  ___|  _ \   / \  | \ | | |_   _| || | |  _ \/ ___|     */
/*     \___ \ / _ \ | |_  | |_) | / _ \ |  \| |   | | | || |_| | | \___ \     */
/*      ___) / ___ \|  _| |  _ < / ___ \| |\  |   | | |__   _| |_| |___) |    */
/*     |____/_/   \_|_|   |_| \_/_/   \_|_| \_|   |_|    |_| |____/|____/     */
/*                                                                            */
/* ************************************************************************** */
 
#include "o2s/file_input_stream.h"
#include "o2s/log.h"
 
#include <errno.h>
#include <iso646.h> // not, and
#include <string.h> // strerror
#include <unistd.h> // read
#include <stdbool.h>
 
#if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 202300L
#   warning including threads.h to have thread_local before C23
#   include <threads.h> // thread_local
#endif

static thread_local bool keep_reading = true;

ssize_t file_single_read(ifstream_t* file)
{
    queue_t*      queue = &file->stream.buffer;
    const size_t  room  = queue_room(queue);
    uint8_t       buffer[room];
    const ssize_t result = read(file->descriptor, buffer, room);
 
    if (result < 0)
        log_error("read returned %zi: %s", result, strerror(errno));
    else if (result > 0 and not queue_push_n(queue, buffer, result))
    { /* This branch is impossible to reach if this thread has exclusive access to the queue, which it should */
        log_error("cannot add %zi characters to the queue, %zu / %zu bytes used", result, queue_count(queue), queue_capacity(queue));
        return -1;
    }
    return result;
}

bool file_accumulate_infinite(ifstream_t* file, size_t count)
{
    while (not istream_has_at_least(&file->stream, count))
        if (not keep_reading or file_single_read(file) < 0)
            return false;
    return true;
}

bool file_accumulate(ifstream_t* file, size_t count)
{
    while (not istream_has_at_least(&file->stream, count))
        if (file_single_read(file) <= 0)
            return false;
    return true;
}

void file_stop_reading(void)
{
    keep_reading = false;
}

void file_resume_reading(void)
{
    keep_reading = true;
}

void file_default_signal_handler(int, siginfo_t*, void*)
{
    file_stop_reading();
}