text: /*
   * Helpers for getting linearized buffers from iov / filling buffers into iovs
   *
   * Copyright IBM, Corp. 2007, 2008
   * Copyright (C) 2010 Red Hat, Inc.
   *
   * Author(s):
   *  Anthony Liguori <aliguori@us.ibm.com>
   *  Amit Shah <amit.shah@redhat.com>
   *  Michael Tokarev <mjt@tls.msk.ru>
   *
   * This work is licensed under the terms of the GNU GPL, version 2.  See
   * the COPYING file in the top-level directory.
   *
   * Contributions after 2012-01-13 are licensed under the terms of the
   * GNU GPL, version 2 or (at your option) any later version.
   */
  
  #include "qemu/osdep.h"
  #include "qemu/iov.h"
  #include "qemu/sockets.h"
  
  size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt,
                           size_t offset, const void *buf, size_t bytes)
  {
      size_t done;
      unsigned int i;
      for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
          if (offset < iov[i].iov_len) {
              size_t len = MIN(iov[i].iov_len - offset, bytes - done);
              memcpy(iov[i].iov_base + offset, buf + done, len);
              done += len;
              offset = 0;
          } else {
              offset -= iov[i].iov_len;
          }
      }
      assert(offset == 0);
      return done;
  }
  
  size_t iov_to_buf_full(const struct iovec *iov, const unsigned int iov_cnt,
                         size_t offset, void *buf, size_t bytes)
  {
      size_t done;
      unsigned int i;
      for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
          if (offset < iov[i].iov_len) {
              size_t len = MIN(iov[i].iov_len - offset, bytes - done);
              memcpy(buf + done, iov[i].iov_base + offset, len);
              done += len;
              offset = 0;
          } else {
              offset -= iov[i].iov_len;
          }
      }
      assert(offset == 0);
      return done;
  }
  
  size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
                    size_t offset, int fillc, size_t bytes)
  {
      size_t done;
      unsigned int i;
      for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
          if (offset < iov[i].iov_len) {
              size_t len = MIN(iov[i].iov_len - offset, bytes - done);
              memset(iov[i].iov_base + offset, fillc, len);
              done += len;
              offset = 0;
          } else {
              offset -= iov[i].iov_len;
          }
      }
      assert(offset == 0);
      return done;
  }
  
  size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt)
  {
      size_t len;
      unsigned int i;
  
      len = 0;
      for (i = 0; i < iov_cnt; i++) {
          len += iov[i].iov_len;
      }
      return len;
  }
  
  /* helper function for iov_send_recv() */
  static ssize_t
  do_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, bool do_send)
  {
  #ifdef CONFIG_POSIX
      ssize_t ret;
      struct msghdr msg;
      memset(&msg, 0, sizeof(msg));
      msg.msg_iov = iov;
      msg.msg_iovlen = iov_cnt;
      do {
          ret = do_send
              ? sendmsg(sockfd, &msg, 0)
              : recvmsg(sockfd, &msg, 0);
      } while (ret < 0 && errno == EINTR);
      return ret;
  #else
      /* else send piece-by-piece */
      /*XXX Note: windows has WSASend() and WSARecv() */
      unsigned i = 0;
      ssize_t ret = 0;
      while (i < iov_cnt) {
          ssize_t r = do_send
              ? send(sockfd, iov[i].iov_base, iov[i].iov_len, 0)
              : recv(sockfd, iov[i].iov_base, iov[i].iov_len, 0);
          if (r > 0) {
              ret += r;
          } else if (!r) {
              break;
          } else if (errno == EINTR) {
              continue;
          } else {
              /* else it is some "other" error,
               * only return if there was no data processed. */
              if (ret == 0) {
                  ret = -1;
              }
              break;
          }
          i++;
      }
      return ret;
  #endif
  }
  
  ssize_t iov_send_recv(int sockfd, const struct iovec *_iov, unsigned iov_cnt,
                        size_t offset, size_t bytes,
                        bool do_send)
  {
      ssize_t total = 0;
      ssize_t ret;
      size_t orig_len, tail;
      unsigned niov;
      struct iovec *local_iov, *iov;
  
      if (bytes <= 0) {
          return 0;
      }
  
      local_iov = g_new0(struct iovec, iov_cnt);
      iov_copy(local_iov, iov_cnt, _iov, iov_cnt, offset, bytes);
      offset = 0;
      iov = local_iov;
  
      while (bytes > 0) {
          /* Find the start position, skipping `offset' bytes:
           * first, skip all full-sized vector elements, */
          for (niov = 0; niov < iov_cnt && offset >= iov[niov].iov_len; ++niov) {
              offset -= iov[niov].iov_len;
          }
  
          /* niov == iov_cnt would only be valid if bytes == 0, which
           * we already ruled out in the loop condition.  */
          assert(niov < iov_cnt);
          iov += niov;
          iov_cnt -= niov;
  
          if (offset) {
              /* second, skip `offset' bytes from the (now) first element,
               * undo it on exit */
              iov[0].iov_base += offset;
              iov[0].iov_len -= offset;
          }
          /* Find the end position skipping `bytes' bytes: */
          /* first, skip all full-sized elements */
          tail = bytes;
          for (niov = 0; niov < iov_cnt && iov[niov].iov_len <= tail; ++niov) {
              tail -= iov[niov].iov_len;
          }
          if (tail) {
              /* second, fixup the last element, and remember the original
               * length */
              assert(niov < iov_cnt);
              assert(iov[niov].iov_len > tail);
              orig_len = iov[niov].iov_len;
              iov[niov++].iov_len = tail;
              ret = do_send_recv(sockfd, iov, niov, do_send);
              /* Undo the changes above before checking for errors */
              iov[niov-1].iov_len = orig_len;
          } else {
              ret = do_send_recv(sockfd, iov, niov, do_send);
          }
          if (offset) {
              iov[0].iov_base -= offset;
              iov[0].iov_len += offset;
          }
  
          if (ret < 0) {
              assert(errno != EINTR);
              g_free(local_iov);
              if (errno == EAGAIN && total > 0) {
                  return total;
              }
              return -1;
          }
  
          if (ret == 0 && !do_send) {
              /* recv returns 0 when the peer has performed an orderly
               * shutdown. */
              break;
          }
  
          /* Prepare for the next iteration */
          offset += ret;
          total += ret;
          bytes -= ret;
      }
  
      g_free(local_iov);
      return total;
  }
  
  
  void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
                   FILE *fp, const char *prefix, size_t limit)
  {
      int v;
      size_t size = 0;
      char *buf;
  
      for (v = 0; v < iov_cnt; v++) {
          size += iov[v].iov_len;
      }
      size = size > limit ? limit : size;
      buf = g_malloc(size);
      iov_to_buf(iov, iov_cnt, 0, buf, size);
      qemu_hexdump(buf, fp, prefix, size);
      g_free(buf);
  }
  
  unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
                   const struct iovec *iov, unsigned int iov_cnt,
                   size_t offset, size_t bytes)
  {
      size_t len;
      unsigned int i, j;
      for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
          if (offset >= iov[i].iov_len) {
              offset -= iov[i].iov_len;
              continue;
          }
          len = MIN(bytes, iov[i].iov_len - offset);
  
          dst_iov[j].iov_base = iov[i].iov_base + offset;
          dst_iov[j].iov_len = len;
          j++;
          bytes -= len;
          offset = 0;
      }
      assert(offset == 0);
      return j;
  }
  
  /* io vectors */
  
  void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
  {
      qiov->iov = g_new(struct iovec, alloc_hint);
      qiov->niov = 0;
      qiov->nalloc = alloc_hint;
      qiov->size = 0;
  }
  
  void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
  {
      int i;
  
      qiov->iov = iov;
      qiov->niov = niov;
      qiov->nalloc = -1;
      qiov->size = 0;
      for (i = 0; i < niov; i++)
          qiov->size += iov[i].iov_len;
  }
  
  void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
  {
      assert(qiov->nalloc != -1);
  
      if (qiov->niov == qiov->nalloc) {
          qiov->nalloc = 2 * qiov->nalloc + 1;
          qiov->iov = g_renew(struct iovec, qiov->iov, qiov->nalloc);
      }
      qiov->iov[qiov->niov].iov_base = base;
      qiov->iov[qiov->niov].iov_len = len;
      qiov->size += len;
      ++qiov->niov;
  }
  
  /*
   * Concatenates (partial) iovecs from src_iov to the end of dst.
   * It starts copying after skipping `soffset' bytes at the
   * beginning of src and adds individual vectors from src to
   * dst copies up to `sbytes' bytes total, or up to the end
   * of src_iov if it comes first.  This way, it is okay to specify
   * very large value for `sbytes' to indicate "up to the end
   * of src".
   * Only vector pointers are processed, not the actual data buffers.
   */
  size_t qemu_iovec_concat_iov(QEMUIOVector *dst,
                               struct iovec *src_iov, unsigned int src_cnt,
                               size_t soffset, size_t sbytes)
  {
      int i;
      size_t done;
  
      if (!sbytes) {
          return 0;
      }
      assert(dst->nalloc != -1);
      for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {
          if (soffset < src_iov[i].iov_len) {
              size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);
              qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);
              done += len;
              soffset = 0;
          } else {
              soffset -= src_iov[i].iov_len;
          }
      }
      assert(soffset == 0); /* offset beyond end of src */
  
      return done;
  }
  
  /*
   * Concatenates (partial) iovecs from src to the end of dst.
   * It starts copying after skipping `soffset' bytes at the
   * beginning of src and adds individual vectors from src to
   * dst copies up to `sbytes' bytes total, or up to the end
   * of src if it comes first.  This way, it is okay to specify
   * very large value for `sbytes' to indicate "up to the end
   * of src".
   * Only vector pointers are processed, not the actual data buffers.
   */
  void qemu_iovec_concat(QEMUIOVector *dst,
                         QEMUIOVector *src, size_t soffset, size_t sbytes)
  {
      qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
  }
  
  /*
   * Check if the contents of the iovecs are all zero
   */
  bool qemu_iovec_is_zero(QEMUIOVector *qiov)
  {
      int i;
      for (i = 0; i < qiov->niov; i++) {
          size_t offs = QEMU_ALIGN_DOWN(qiov->iov[i].iov_len, 4 * sizeof(long));
          uint8_t *ptr = qiov->iov[i].iov_base;
          if (offs && !buffer_is_zero(qiov->iov[i].iov_base, offs)) {
              return false;
          }
          for (; offs < qiov->iov[i].iov_len; offs++) {
              if (ptr[offs]) {
                  return false;
              }
          }
      }
      return true;
  }
  
  void qemu_iovec_destroy(QEMUIOVector *qiov)
  {
      assert(qiov->nalloc != -1);
  
      qemu_iovec_reset(qiov);
      g_free(qiov->iov);
      qiov->nalloc = 0;
      qiov->iov = NULL;
  }
  
  void qemu_iovec_reset(QEMUIOVector *qiov)
  {
      assert(qiov->nalloc != -1);
  
      qiov->niov = 0;
      qiov->size = 0;
  }
  
  size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
                           void *buf, size_t bytes)
  {
      return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
  }
  
  size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
                             const void *buf, size_t bytes)
  {
      return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
  }
  
  size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
                           int fillc, size_t bytes)
  {
      return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
  }
  
  /**
   * Check that I/O vector contents are identical
   *
   * The IO vectors must have the same structure (same length of all parts).
   * A typical usage is to compare vectors created with qemu_iovec_clone().
   *
   * @a:          I/O vector
   * @b:          I/O vector
   * @ret:        Offset to first mismatching byte or -1 if match
   */
  ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b)
  {
      int i;
      ssize_t offset = 0;
  
      assert(a->niov == b->niov);
      for (i = 0; i < a->niov; i++) {
          size_t len = 0;
          uint8_t *p = (uint8_t *)a->iov[i].iov_base;
          uint8_t *q = (uint8_t *)b->iov[i].iov_base;
  
          assert(a->iov[i].iov_len == b->iov[i].iov_len);
          while (len < a->iov[i].iov_len && *p++ == *q++) {
              len++;
          }
  
          offset += len;
  
          if (len != a->iov[i].iov_len) {
              return offset;
          }
      }
      return -1;
  }
  
  typedef struct {
      int src_index;
      struct iovec *src_iov;
      void *dest_base;
  } IOVectorSortElem;
  
  static int sortelem_cmp_src_base(const void *a, const void *b)
  {
      const IOVectorSortElem *elem_a = a;
      const IOVectorSortElem *elem_b = b;
  
      /* Don't overflow */
      if (elem_a->src_iov->iov_base < elem_b->src_iov->iov_base) {
          return -1;
      } else if (elem_a->src_iov->iov_base > elem_b->src_iov->iov_base) {
          return 1;
      } else {
          return 0;
      }
  }
  
  static int sortelem_cmp_src_index(const void *a, const void *b)
  {
      const IOVectorSortElem *elem_a = a;
      const IOVectorSortElem *elem_b = b;
  
      return elem_a->src_index - elem_b->src_index;
  }
  
  /**
   * Copy contents of I/O vector
   *
   * The relative relationships of overlapping iovecs are preserved.  This is
   * necessary to ensure identical semantics in the cloned I/O vector.
   */
  void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf)
  {
      IOVectorSortElem sortelems[src->niov];
      void *last_end;
      int i;
  
      /* Sort by source iovecs by base address */
      for (i = 0; i < src->niov; i++) {
          sortelems[i].src_index = i;
          sortelems[i].src_iov = &src->iov[i];
      }
      qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base);
  
      /* Allocate buffer space taking into account overlapping iovecs */
      last_end = NULL;
      for (i = 0; i < src->niov; i++) {
          struct iovec *cur = sortelems[i].src_iov;
          ptrdiff_t rewind = 0;
  
          /* Detect overlap */
          if (last_end && last_end > cur->iov_base) {
              rewind = last_end - cur->iov_base;
          }
  
          sortelems[i].dest_base = buf - rewind;
          buf += cur->iov_len - MIN(rewind, cur->iov_len);
          last_end = MAX(cur->iov_base + cur->iov_len, last_end);
      }
  
      /* Sort by source iovec index and build destination iovec */
      qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index);
      for (i = 0; i < src->niov; i++) {
          qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len);
      }
  }
  
  size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
                           size_t bytes)
  {
      size_t total = 0;
      struct iovec *cur;
  
      for (cur = *iov; *iov_cnt > 0; cur++) {
          if (cur->iov_len > bytes) {
              cur->iov_base += bytes;
              cur->iov_len -= bytes;
              total += bytes;
              break;
          }
  
          bytes -= cur->iov_len;
          total += cur->iov_len;
          *iov_cnt -= 1;
      }
  
      *iov = cur;
      return total;
  }
  
  size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
                          size_t bytes)
  {
      size_t total = 0;
      struct iovec *cur;
  
      if (*iov_cnt == 0) {
          return 0;
      }
  
      cur = iov + (*iov_cnt - 1);
  
      while (*iov_cnt > 0) {
          if (cur->iov_len > bytes) {
              cur->iov_len -= bytes;
              total += bytes;
              break;
          }
  
          bytes -= cur->iov_len;
          total += cur->iov_len;
          cur--;
          *iov_cnt -= 1;
      }
  
      return total;
  }
  
  void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes)
  {
      size_t total;
      unsigned int niov = qiov->niov;
  
      assert(qiov->size >= bytes);
      total = iov_discard_back(qiov->iov, &niov, bytes);
      assert(total == bytes);
  
      qiov->niov = niov;
      qiov->size -= bytes;
  }
  