file.c

/*

  Copyright (c) 2016 Paulo Faria

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"),
  to deal in the Software without restriction, including without limitation
  the rights to use, copy, modify, merge, publish, distribute, sublicense,
  and/or sell copies of the Software, and to permit persons to whom
  the Software is furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included
  in all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  IN THE SOFTWARE.

*/

#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>

#include "libmill.h"
#include "utils.h"

#ifndef MILL_FILE_BUFLEN
#define MILL_FILE_BUFLEN (4096)
#endif

struct mill_file {
    int fd;
    size_t ifirst;
    size_t ilen;
    size_t olen;
    char ibuf[MILL_FILE_BUFLEN];
    char obuf[MILL_FILE_BUFLEN];
};

static void mill_filetune(int fd) {
    /* Make the file descriptor non-blocking. */
    int opt = fcntl(fd, F_GETFL, 0);
    if (opt == -1)
        opt = 0;
    int rc = fcntl(fd, F_SETFL, opt | O_NONBLOCK);
    mill_assert(rc != -1);
}


mfile mfopen(const char *pathname, int flags, mode_t mode) {
    /* Open the file. */
    int fd = open(pathname, flags, mode);
    if (fd == -1)
        return NULL;
    mill_filetune(fd);

    /* Create the object. */
    struct mill_file *f = malloc(sizeof(struct mill_file));
    if(!f) {
        fdclean(fd);
        close(fd);
        errno = ENOMEM;
        return NULL;
    }
    f->fd = fd;
    f->ifirst = 0;
    f->ilen = 0;
    f->olen = 0;
    errno = 0;
    return f;
}

size_t mfwrite(mfile f, const void *buf, size_t len, int64_t deadline) {
    /* If it fits into the output buffer copy it there and be done. */
    if(f->olen + len <= MILL_FILE_BUFLEN) {
        memcpy(&f->obuf[f->olen], buf, len);
        f->olen += len;
        errno = 0;
        return len;
    }

    /* If it doesn't fit, flush the output buffer first. */
    mfflush(f, deadline);
    if(errno != 0)
        return 0;

    /* Try to fit it into the buffer once again. */
    if(f->olen + len <= MILL_FILE_BUFLEN) {
        memcpy(&f->obuf[f->olen], buf, len);
        f->olen += len;
        errno = 0;
        return len;
    }

    /* The data chunk to send is longer than the output buffer.
     Let's do the writing in-place. */
    char *pos = (char*)buf;
    size_t remaining = len;
    while(remaining) {
        ssize_t sz = write(f->fd, pos, remaining);
        if(sz == -1) {
            if(errno != EAGAIN && errno != EWOULDBLOCK)
                return 0;
            int rc = fdwait(f->fd, FDW_OUT, deadline);
            if(rc == 0) {
                errno = ETIMEDOUT;
                return len - remaining;
            }
            mill_assert(rc == FDW_OUT);
            continue;
        }
        pos += sz;
        remaining -= sz;
    }
    return len;
}

void mfflush(mfile f, int64_t deadline) {
    if(!f->olen) {
        errno = 0;
        return;
    }
    char *pos = f->obuf;
    size_t remaining = f->olen;
    while(remaining) {
        ssize_t sz = write(f->fd, pos, remaining);
        if(sz == -1) {
            if(errno != EAGAIN && errno != EWOULDBLOCK)
                return;
            int rc = fdwait(f->fd, FDW_OUT, deadline);
            if(rc == 0) {
                errno = ETIMEDOUT;
                return;
            }
            mill_assert(rc == FDW_OUT);
            continue;
        }
        pos += sz;
        remaining -= sz;
    }
    f->olen = 0;
    errno = 0;
}

size_t mfread(mfile f, void *buf, size_t len, int64_t deadline) {
    /* If there's enough data in the buffer it's easy. */
    if(f->ilen >= len) {
        memcpy(buf, &f->ibuf[f->ifirst], len);
        f->ifirst += len;
        f->ilen -= len;
        errno = 0;
        return len;
    }

    /* Let's move all the data from the buffer first. */
    char *pos = (char*)buf;
    size_t remaining = len;
    memcpy(pos, &f->ibuf[f->ifirst], f->ilen);
    pos += f->ilen;
    remaining -= f->ilen;
    f->ifirst = 0;
    f->ilen = 0;

    mill_assert(remaining);
    while(1) {
        if(remaining > MILL_FILE_BUFLEN) {
            /* If we still have a lot to read try to read it in one go directly
             into the destination buffer. */
            ssize_t sz = read(f->fd, pos, remaining);
            if(!sz) {
                return len - remaining;
            }
            if(sz == -1) {
                if(errno != EAGAIN && errno != EWOULDBLOCK)
                    return len - remaining;
                sz = 0;
            }
            if((size_t)sz == remaining) {
                errno = 0;
                return len;
            }
            pos += sz;
            remaining -= sz;
            if (sz != 0 && mfeof(f)) {
                return len - remaining;
            }
        }
        else {
            /* If we have just a little to read try to read the full connection
             buffer to minimise the number of system calls. */
            ssize_t sz = read(f->fd, f->ibuf, MILL_FILE_BUFLEN);
            if(!sz) {
                return len - remaining;
            }
            if(sz == -1) {
                if(errno != EAGAIN && errno != EWOULDBLOCK)
                    return len - remaining;
                sz = 0;
            }
            if((size_t)sz < remaining) {
                memcpy(pos, f->ibuf, sz);
                pos += sz;
                remaining -= sz;
                f->ifirst = 0;
                f->ilen = 0;
            }
            else {
                memcpy(pos, f->ibuf, remaining);
                f->ifirst = remaining;
                f->ilen = sz - remaining;
                errno = 0;
                return len;
            }
            if (sz != 0 && mfeof(f)) {
                return len - remaining;
            }
        }

        /* Wait till there's more data to read. */
        int res = fdwait(f->fd, FDW_IN, deadline);
        if (!res) {
            errno = ETIMEDOUT;
            return len - remaining;
        }
    }
}

void mfclose(mfile f) {
    fdclean(f->fd);
    int rc = close(f->fd);
    mill_assert(rc == 0);
    free(f);
    return;
}

off_t mftell(mfile f) {
    return lseek(f->fd, 0, SEEK_CUR) - f->ilen;
}

off_t mfseek(mfile f, off_t offset) {
    f->ifirst = 0;
    f->ilen = 0;
    f->olen = 0;
    return lseek(f->fd, offset, SEEK_SET);
}

int mfeof(mfile f) {
    off_t current = lseek(f->fd, 0, SEEK_CUR);
    if (current == -1)
        return -1;
    off_t eof = lseek(f->fd, 0, SEEK_END);
    if (eof == -1)
        return -1;
    off_t res = lseek(f->fd, current, SEEK_SET);
    if (res == -1)
        return -1;
    return (current == eof);
}

mfile mill_mfin(void) {
    static struct mill_file f = {-1, 0, 0, 0};
    if(mill_slow(f.fd < 0)) {
        mill_filetune(STDIN_FILENO);
        f.fd = STDIN_FILENO;
    }
    return &f;
}

mfile mill_mfout(void) {
    static struct mill_file f = {-1, 0, 0, 0};
    if(mill_slow(f.fd < 0)) {
        mill_filetune(STDOUT_FILENO);
        f.fd = STDOUT_FILENO;
    }
    return &f;
}

mfile mill_mferr(void) {
    static struct mill_file f = {-1, 0, 0, 0};
    if(mill_slow(f.fd < 0)) {
        mill_filetune(STDERR_FILENO);
        f.fd = STDERR_FILENO;
    }
    return &f;
}