third_party/ulib/musl/src/stdio/__stdio_read.c

#include "stdio_impl.h"
#include <sys/uio.h>

size_t __stdio_read(FILE* f, unsigned char* buf, size_t len) {
    struct iovec iov[2] = {{.iov_base = buf, .iov_len = len - !!f->buf_size},
                           {.iov_base = f->buf, .iov_len = f->buf_size}};
    ssize_t cnt = readv(f->fd, iov, 2);
    if (cnt <= 0) {
        f->flags |= F_EOF ^ ((F_ERR ^ F_EOF) & cnt);
        return cnt;
    }
    if (cnt <= iov[0].iov_len)
        return cnt;
    cnt -= iov[0].iov_len;
    f->rpos = f->buf;
    f->rend = f->buf + cnt;
    if (f->buf_size)
        buf[len - 1] = *f->rpos++;
    return len;
}