/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil ; -*- */
/*
 *
 *   Copyright (C) 1997 University of Chicago.
 *   See COPYRIGHT notice in top-level directory.
 */

#include "adio.h"
#include "adio_extern.h"

#define ADIOI_BUFFERED_READ                                             \
    {                                                                   \
        if (req_off >= readbuf_off + readbuf_len) {                     \
            readbuf_off = req_off;                                      \
            readbuf_len = (unsigned) (MPL_MIN(max_bufsize, end_offset-readbuf_off+1)); \
            ADIO_ReadContig(fd, readbuf, readbuf_len, MPI_BYTE,         \
                            ADIO_EXPLICIT_OFFSET, readbuf_off, &status1, error_code); \
            if (*error_code != MPI_SUCCESS) return;                     \
        }                                                               \
        while (req_len > readbuf_off + readbuf_len - req_off) {         \
            ADIOI_Assert((readbuf_off + readbuf_len - req_off) == (int) (readbuf_off + readbuf_len - req_off)); \
            partial_read = (int) (readbuf_off + readbuf_len - req_off); \
            tmp_buf = (char *) ADIOI_Malloc(partial_read);              \
            memcpy(tmp_buf, readbuf+readbuf_len-partial_read, partial_read); \
            ADIOI_Free(readbuf);                                        \
            readbuf = (char *) ADIOI_Malloc(partial_read + max_bufsize); \
            memcpy(readbuf, tmp_buf, partial_read);                     \
            ADIOI_Free(tmp_buf);                                        \
            readbuf_off += readbuf_len-partial_read;                    \
            readbuf_len = (unsigned) (partial_read + MPL_MIN(max_bufsize, \
                                                             end_offset-readbuf_off+1)); \
            ADIO_ReadContig(fd, readbuf+partial_read, readbuf_len-partial_read, \
                            MPI_BYTE, ADIO_EXPLICIT_OFFSET, readbuf_off+partial_read, \
                            &status1, error_code);                      \
            if (*error_code != MPI_SUCCESS) return;                     \
        }                                                               \
        ADIOI_Assert(req_len == (size_t)req_len);                       \
        memcpy((char *)buf + userbuf_off, readbuf+req_off-readbuf_off, req_len); \
    }


void ADIOI_GEN_ReadStrided(ADIO_File fd, void *buf, int count,
                           MPI_Datatype datatype, int file_ptr_type,
                           ADIO_Offset offset, ADIO_Status * status, int
                           *error_code)
{


/* offset is in units of etype relative to the filetype. */

    ADIOI_Flatlist_node *flat_buf, *flat_file;
    ADIO_Offset i_offset, new_brd_size, brd_size, size;
    int i, j, k, st_index = 0;
    MPI_Count num, bufsize;
    int n_etypes_in_filetype;
    ADIO_Offset n_filetypes, etype_in_filetype, st_n_filetypes, size_in_filetype;
    ADIO_Offset abs_off_in_filetype = 0, new_frd_size, frd_size = 0, st_frd_size;
    MPI_Count filetype_size, etype_size, buftype_size, partial_read;
    MPI_Aint filetype_extent, buftype_extent;
    int buf_count, buftype_is_contig, filetype_is_contig;
    ADIO_Offset userbuf_off, req_len, sum;
    ADIO_Offset off, req_off, disp, end_offset = 0, readbuf_off, start_off;
    char *readbuf, *tmp_buf, *value;
    int info_flag;
    unsigned max_bufsize, readbuf_len;
    ADIO_Status status1;

    if (fd->hints->ds_read == ADIOI_HINT_DISABLE) {
        /* if user has disabled data sieving on reads, use naive
         * approach instead.
         */
        ADIOI_GEN_ReadStrided_naive(fd,
                                    buf,
                                    count, datatype, file_ptr_type, offset, status, error_code);
        return;
    }

    *error_code = MPI_SUCCESS;  /* changed below if error */

    ADIOI_Datatype_iscontig(datatype, &buftype_is_contig);
    ADIOI_Datatype_iscontig(fd->filetype, &filetype_is_contig);

    MPI_Type_size_x(fd->filetype, &filetype_size);
    if (!filetype_size) {
#ifdef HAVE_STATUS_SET_BYTES
        MPIR_Status_set_bytes(status, datatype, 0);
#endif
        *error_code = MPI_SUCCESS;
        return;
    }

    MPI_Type_extent(fd->filetype, &filetype_extent);
    MPI_Type_size_x(datatype, &buftype_size);
    MPI_Type_extent(datatype, &buftype_extent);
    etype_size = fd->etype_size;

    ADIOI_Assert((buftype_size * count) ==
                 ((ADIO_Offset) (MPI_Count) buftype_size * (ADIO_Offset) count));
    bufsize = buftype_size * count;

/* get max_bufsize from the info object. */

    value = (char *) ADIOI_Malloc((MPI_MAX_INFO_VAL + 1) * sizeof(char));
    ADIOI_Info_get(fd->info, "ind_rd_buffer_size", MPI_MAX_INFO_VAL, value, &info_flag);
    max_bufsize = atoi(value);
    ADIOI_Free(value);


    if (!buftype_is_contig && filetype_is_contig) {

/* noncontiguous in memory, contiguous in file. */

        flat_buf = ADIOI_Flatten_and_find(datatype);

        off = (file_ptr_type == ADIO_INDIVIDUAL) ? fd->fp_ind :
            fd->disp + (ADIO_Offset) etype_size *offset;

        start_off = off;
        end_offset = off + bufsize - 1;
        readbuf_off = off;
        readbuf = (char *) ADIOI_Malloc(max_bufsize);
        readbuf_len = (unsigned) (MPL_MIN(max_bufsize, end_offset - readbuf_off + 1));

/* if atomicity is true, lock (exclusive) the region to be accessed */
        if ((fd->atomicity) && ADIO_Feature(fd, ADIO_LOCKS))
            ADIOI_WRITE_LOCK(fd, start_off, SEEK_SET, end_offset - start_off + 1);

        ADIO_ReadContig(fd, readbuf, readbuf_len, MPI_BYTE,
                        ADIO_EXPLICIT_OFFSET, readbuf_off, &status1, error_code);
        if (*error_code != MPI_SUCCESS)
            return;

        for (j = 0; j < count; j++) {
            for (i = 0; i < flat_buf->count; i++) {
                userbuf_off = (ADIO_Offset) j *(ADIO_Offset) buftype_extent + flat_buf->indices[i];
                req_off = off;
                req_len = flat_buf->blocklens[i];
                ADIOI_BUFFERED_READ off += flat_buf->blocklens[i];
            }
        }

        if ((fd->atomicity) && ADIO_Feature(fd, ADIO_LOCKS))
            ADIOI_UNLOCK(fd, start_off, SEEK_SET, end_offset - start_off + 1);

        if (file_ptr_type == ADIO_INDIVIDUAL)
            fd->fp_ind = off;

        ADIOI_Free(readbuf);
    }

    else {      /* noncontiguous in file */

        flat_file = ADIOI_Flatten_and_find(fd->filetype);
        disp = fd->disp;

        if (file_ptr_type == ADIO_INDIVIDUAL) {
            /* Wei-keng reworked type processing to be a bit more efficient */
            offset = fd->fp_ind - disp;
            n_filetypes = (offset - flat_file->indices[0]) / filetype_extent;
            offset -= (ADIO_Offset) n_filetypes *filetype_extent;
            /* now offset is local to this extent */

            /* find the block where offset is located, skip blocklens[i]==0 */
            for (i = 0; i < flat_file->count; i++) {
                ADIO_Offset dist;
                if (flat_file->blocklens[i] == 0)
                    continue;
                dist = flat_file->indices[i] + flat_file->blocklens[i] - offset;
                /* frd_size is from offset to the end of block i */
                if (dist == 0) {
                    i++;
                    offset = flat_file->indices[i];
                    frd_size = flat_file->blocklens[i];
                    break;
                }
                if (dist > 0) {
                    frd_size = dist;
                    break;
                }
            }
            st_index = i;       /* starting index in flat_file->indices[] */
            offset += disp + (ADIO_Offset) n_filetypes *filetype_extent;
        } else {
            n_etypes_in_filetype = filetype_size / etype_size;
            n_filetypes = offset / n_etypes_in_filetype;
            etype_in_filetype = offset % n_etypes_in_filetype;
            size_in_filetype = etype_in_filetype * etype_size;

            sum = 0;
            for (i = 0; i < flat_file->count; i++) {
                sum += flat_file->blocklens[i];
                if (sum > size_in_filetype) {
                    st_index = i;
                    frd_size = sum - size_in_filetype;
                    abs_off_in_filetype = flat_file->indices[i] +
                        size_in_filetype - (sum - flat_file->blocklens[i]);
                    break;
                }
            }

            /* abs. offset in bytes in the file */
            offset = disp + (ADIO_Offset) n_filetypes *filetype_extent + abs_off_in_filetype;
        }

        start_off = offset;

        /* Wei-keng Liao: read request is within a single flat_file contig
         * block e.g. with subarray types that actually describe the whole
         * array */
        if (buftype_is_contig && bufsize <= frd_size) {
            /* a count of bytes can overflow. operate on original type instead */
            ADIO_ReadContig(fd, buf, count, datatype, ADIO_EXPLICIT_OFFSET,
                            offset, status, error_code);

            if (file_ptr_type == ADIO_INDIVIDUAL) {
                /* update MPI-IO file pointer to point to the first byte that
                 * can be accessed in the fileview. */
                fd->fp_ind = offset + bufsize;
                if (bufsize == frd_size) {
                    do {
                        st_index++;
                        if (st_index == flat_file->count) {
                            st_index = 0;
                            n_filetypes++;
                        }
                    } while (flat_file->blocklens[st_index] == 0);
                    fd->fp_ind = disp + flat_file->indices[st_index]
                        + n_filetypes * filetype_extent;
                }
            }
            fd->fp_sys_posn = -1;       /* set it to null. */
#ifdef HAVE_STATUS_SET_BYTES
            MPIR_Status_set_bytes(status, datatype, bufsize);
#endif
            return;
        }

        /* Calculate end_offset, the last byte-offset that will be accessed.
         * e.g., if start_offset=0 and 100 bytes to be read, end_offset=99 */

        st_frd_size = frd_size;
        st_n_filetypes = n_filetypes;
        i_offset = 0;
        j = st_index;
        off = offset;
        frd_size = MPL_MIN(st_frd_size, bufsize);
        while (i_offset < bufsize) {
            i_offset += frd_size;
            end_offset = off + frd_size - 1;

            j = (j + 1) % flat_file->count;
            n_filetypes += (j == 0) ? 1 : 0;
            while (flat_file->blocklens[j] == 0) {
                j = (j + 1) % flat_file->count;
                n_filetypes += (j == 0) ? 1 : 0;
            }
            off = disp + flat_file->indices[j] + n_filetypes * (ADIO_Offset) filetype_extent;
            frd_size = MPL_MIN(flat_file->blocklens[j], bufsize - i_offset);
        }

/* if atomicity is true, lock (exclusive) the region to be accessed */
        if ((fd->atomicity) && ADIO_Feature(fd, ADIO_LOCKS))
            ADIOI_WRITE_LOCK(fd, start_off, SEEK_SET, end_offset - start_off + 1);

        readbuf_off = 0;
        readbuf_len = 0;
        readbuf = (char *) ADIOI_Malloc(max_bufsize);

        if (buftype_is_contig && !filetype_is_contig) {

/* contiguous in memory, noncontiguous in file. should be the most
   common case. */

            i_offset = 0;
            j = st_index;
            off = offset;
            n_filetypes = st_n_filetypes;
            frd_size = MPL_MIN(st_frd_size, bufsize);
            while (i_offset < bufsize) {
                if (frd_size) {
                    /* TYPE_UB and TYPE_LB can result in
                     * frd_size = 0. save system call in such cases */
                    /* lseek(fd->fd_sys, off, SEEK_SET);
                     * err = read(fd->fd_sys, ((char *) buf) + i, frd_size); */

                    req_off = off;
                    req_len = frd_size;
                    userbuf_off = i_offset;
                ADIOI_BUFFERED_READ}
                i_offset += frd_size;

                if (off + frd_size < disp + flat_file->indices[j] +
                    flat_file->blocklens[j] + n_filetypes * (ADIO_Offset) filetype_extent)
                    off += frd_size;
                /* did not reach end of contiguous block in filetype.
                 * no more I/O needed. off is incremented by frd_size. */
                else {
                    j = (j + 1) % flat_file->count;
                    n_filetypes += (j == 0) ? 1 : 0;
                    while (flat_file->blocklens[j] == 0) {
                        j = (j + 1) % flat_file->count;
                        n_filetypes += (j == 0) ? 1 : 0;
                    }
                    off = disp + flat_file->indices[j] +
                        n_filetypes * (ADIO_Offset) filetype_extent;
                    frd_size = MPL_MIN(flat_file->blocklens[j], bufsize - i_offset);
                }
            }
        } else {
/* noncontiguous in memory as well as in file */

            flat_buf = ADIOI_Flatten_and_find(datatype);

            k = num = buf_count = 0;
            i_offset = flat_buf->indices[0];
            j = st_index;
            off = offset;
            n_filetypes = st_n_filetypes;
            frd_size = st_frd_size;
            brd_size = flat_buf->blocklens[0];

            while (num < bufsize) {
                size = MPL_MIN(frd_size, brd_size);
                if (size) {
                    /* lseek(fd->fd_sys, off, SEEK_SET);
                     * err = read(fd->fd_sys, ((char *) buf) + i, size); */

                    req_off = off;
                    req_len = size;
                    userbuf_off = i_offset;
                ADIOI_BUFFERED_READ}

                new_frd_size = frd_size;
                new_brd_size = brd_size;

                if (size == frd_size) {
/* reached end of contiguous block in file */
                    j = (j + 1) % flat_file->count;
                    n_filetypes += (j == 0) ? 1 : 0;
                    while (flat_file->blocklens[j] == 0) {
                        j = (j + 1) % flat_file->count;
                        n_filetypes += (j == 0) ? 1 : 0;
                    }
                    off = disp + flat_file->indices[j] +
                        n_filetypes * (ADIO_Offset) filetype_extent;

                    new_frd_size = flat_file->blocklens[j];
                    if (size != brd_size) {
                        i_offset += size;
                        new_brd_size -= size;
                    }
                }

                if (size == brd_size) {
/* reached end of contiguous block in memory */

                    k = (k + 1) % flat_buf->count;
                    buf_count++;
                    i_offset =
                        ((ADIO_Offset) buftype_extent *
                         (ADIO_Offset) (buf_count / flat_buf->count) + flat_buf->indices[k]);
                    new_brd_size = flat_buf->blocklens[k];
                    if (size != frd_size) {
                        off += size;
                        new_frd_size -= size;
                    }
                }
                ADIOI_Assert(((ADIO_Offset) num + size) == (unsigned) (num + size));
                num += size;
                frd_size = new_frd_size;
                brd_size = new_brd_size;
            }
        }

        if ((fd->atomicity) && ADIO_Feature(fd, ADIO_LOCKS))
            ADIOI_UNLOCK(fd, start_off, SEEK_SET, end_offset - start_off + 1);

        if (file_ptr_type == ADIO_INDIVIDUAL)
            fd->fp_ind = off;

        ADIOI_Free(readbuf);    /* malloced in the buffered_read macro */
    }

    fd->fp_sys_posn = -1;       /* set it to null. */

#ifdef HAVE_STATUS_SET_BYTES
    MPIR_Status_set_bytes(status, datatype, bufsize);
/* This is a temporary way of filling in status. The right way is to
   keep track of how much data was actually read and placed in buf
   by ADIOI_BUFFERED_READ. */
#endif

}
