#include "buffer.h"

#include <unistd.h>

#include "byte.h"
#include "error.h"
#include "str.h"

/**
  @file buffer.c
  @author djb
  @brief input/output routines
*/

void buffer_init(buffer *s, ssize_t (*op)(), int fd, char *buf, size_t len)
{
  s->x = buf;
  s->fd = fd;
  s->op = op;
  s->p = 0;
  s->n = len;
}

static ssize_t buffer_0_read(int fd, char *buf, size_t len)
{
  if (buffer_flush(buffer_1) == -1) return -1;
  return read(fd, buf, len);
}

ssize_t buffer_unixread(int fd, char *buf, size_t len)
{
  return (ssize_t)read(fd, buf, len);
}

ssize_t buffer_unixwrite(int fd, char *buf, size_t len)
{
  return (ssize_t)write(fd, buf, len);
}

char buffer_0_space[BUFFER_INSIZE];
static buffer it0 = BUFFER_INIT(buffer_0_read, 0, buffer_0_space, sizeof(buffer_0_space));
buffer *buffer_0 = &it0;

char buffer_1_space[BUFFER_OUTSIZE];
static buffer it1 = BUFFER_INIT(buffer_unixwrite, 1, buffer_1_space, sizeof(buffer_1_space));
buffer *buffer_1 = &it1;

char buffer_2_space[BUFFER_OUTSIZE];
static buffer it2 = BUFFER_INIT(buffer_unixwrite, 2, buffer_2_space, sizeof(buffer_2_space));
buffer *buffer_2 = &it2;

char buffer_0_small[BUFFER_SMALL];
static buffer is0 = BUFFER_INIT(buffer_0_read, 0, buffer_0_small, sizeof(buffer_0_small));
buffer *buffer_0small = &is0;

char buffer_1_small[BUFFER_SMALL];
static buffer is1 = BUFFER_INIT(buffer_unixwrite, 1, buffer_1_small, sizeof(buffer_1_small));
buffer *buffer_1small = &is1;

char buffer_2_small[BUFFER_SMALL];
static buffer is2 = BUFFER_INIT(buffer_unixwrite, 2, buffer_2_small, sizeof(buffer_2_small));
buffer *buffer_2small = &is2;

int buffer_copy(buffer *bout, buffer *bin)
{
  int n;
  char *x;

  for (;;) {
    n = buffer_feed(bin);
    if (n < 0) return -2;
    if (!n) return 0;
    x = buffer_PEEK(bin);
    if (buffer_put(bout, x, n) == -1) return -3;
    buffer_SEEK(bin, n);
  }
}

static int oneread(ssize_t (*op)(), int fd, char *buf, size_t len)
{
  int r;

  for (;;) {
    r = op(fd, buf, len);
    if (r == -1)
      if (errno == EINTR) continue;
    return r;
  }
}

static int getthis(buffer *s, char *buf, size_t len)
{
  if (len > s->p) len = s->p;
  s->p -= len;
  byte_copy(buf, len, s->x + s->n);
  s->n += len;
  return len;
}

int buffer_feed(buffer *s)
{
  int r;

  if (s->p) return s->p;
  r = oneread(s->op, s->fd, s->x, s->n);
  if (r <= 0) return r;
  s->p = r;
  s->n -= r;
  if (s->n > 0) byte_copyr(s->x + s->n, r, s->x);
  return r;
}

int buffer_bget(buffer *s, char *buf, size_t len)
{
  int r;

  if (s->p > 0) return getthis(s, buf, len);
  if (s->n <= len) return oneread(s->op, s->fd, buf, s->n);
  r = buffer_feed(s);
  if (r <= 0) return r;
  return getthis(s, buf, len);
}

int buffer_get(buffer *s, char *buf, size_t len)
{
  int r;

  if (s->p > 0) return getthis(s, buf, len);
  if (s->n <= len) return oneread(s->op, s->fd, buf, len);
  r = buffer_feed(s);
  if (r <= 0) return r;
  return getthis(s, buf, len);
}

char *buffer_peek(buffer *s)
{
  return s->x + s->n;
}

void buffer_seek(buffer *s, size_t len)
{
  s->n += len;
  s->p -= len;
}

static int allwrite(ssize_t (*op)(), int fd, const char *buf, size_t len)
{
  int w;

  while (len) {
    w = op(fd, buf, len);
    if (w == -1) {
      if (errno == EINTR) continue;
      return -1; /* note that some data may have been written */
    }
    if (w == 0) /* luser's fault */
      ;
    buf += w;
    len -= w;
  }
  return 0;
}

int buffer_flush(buffer *s)
{
  int p;

  p = s->p;
  if (!p) return 0;
  s->p = 0;
  return allwrite(s->op, s->fd, s->x, p);
}

int buffer_putalign(buffer *s, const char *buf, size_t len)
{
  unsigned int n;

  while (len > (n = s->n - s->p)) {
    byte_copy(s->x + s->p, n, buf);
    s->p += n;
    buf += n;
    len -= n;
    if (buffer_flush(s) == -1) return -1;
  }
  /* now len <= s->n - s->p */
  byte_copy(s->x + s->p, len, buf);
  s->p += len;
  return 0;
}

int buffer_put(buffer *s, const char *buf, size_t len)
{
  unsigned int n;

  n = s->n;
  if (len > n - s->p) {
    if (buffer_flush(s) == -1) return -1;
    /* now s->p == 0 */
    if (n < BUFFER_OUTSIZE) n = BUFFER_OUTSIZE;
    while (len > s->n) {
      if (n > len) n = len;
      if (allwrite(s->op, s->fd, buf, n) == -1) return -1;
      buf += n;
      len -= n;
    }
  }
  /* now len <= s->n - s->p */
  byte_copy(s->x + s->p, len, buf);
  s->p += len;
  return 0;
}

int buffer_putflush(buffer *s, const char *buf, size_t len)
{
  if (buffer_flush(s) == -1) return -1;
  return allwrite(s->op, s->fd, buf, len);
}

int buffer_putsalign(buffer *s, const char *buf)
{
  return buffer_putalign(s, buf, str_len(buf));
}

int buffer_puts(buffer *s, const char *buf)
{
  return buffer_put(s, buf, str_len(buf));
}

int buffer_putsflush(buffer *s, const char *buf)
{
  return buffer_putflush(s, buf, str_len(buf));
}