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  Every copy of AFPL Ghostscript must include a copy of the License, normally
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*/

/*$Id: zfproc.c,v 1.4.2.4 2000/12/02 19:55:31 raph Exp $ */
/* Procedure-based filter stream support */
#include "memory_.h"
#include "ghost.h"
#include "oper.h"               /* for ifilter.h */
#include "estack.h"
#include "gsstruct.h"
#include "ialloc.h"
#include "istruct.h"            /* for RELOC_REF_VAR */
#include "stream.h"
#include "strimpl.h"
#include "ifilter.h"
#include "files.h"
#include "store.h"

/* ---------------- Generic ---------------- */

/* GC procedures */
private 
CLEAR_MARKS_PROC(sproc_clear_marks)
{
    stream_proc_state *const pptr = vptr;

    r_clear_attrs(&pptr->proc, l_mark);
    r_clear_attrs(&pptr->data, l_mark);
}
private 
ENUM_PTRS_WITH(sproc_enum_ptrs, stream_proc_state *pptr) return 0;
case 0:
ENUM_RETURN_REF(&pptr->proc);
case 1:
ENUM_RETURN_REF(&pptr->data);
ENUM_PTRS_END
private RELOC_PTRS_WITH(sproc_reloc_ptrs, stream_proc_state *pptr);
RELOC_REF_VAR(pptr->proc);
r_clear_attrs(&pptr->proc, l_mark);
RELOC_REF_VAR(pptr->data);
r_clear_attrs(&pptr->data, l_mark);
RELOC_PTRS_END

/* Structure type for procedure-based streams. */
private_st_stream_proc_state();

/* Allocate and open a procedure-based filter. */
/* The caller must have checked that *sop is a procedure. */
private int
s_proc_init(ref * sop, stream ** psstrm, uint mode,
            const stream_template * temp, const stream_procs * procs,
            gs_ref_memory_t *imem)
{
    gs_memory_t *const mem = (gs_memory_t *)imem;
    stream *sstrm = file_alloc_stream(mem, "s_proc_init(stream)");
    stream_proc_state *state = (stream_proc_state *)
        s_alloc_state(mem, &st_sproc_state, "s_proc_init(state)");

    if (sstrm == 0 || state == 0) {
        gs_free_object(mem, state, "s_proc_init(state)");
        /*gs_free_object(mem, sstrm, "s_proc_init(stream)"); *//* just leave it on the file list */
        return_error(e_VMerror);
    }
    s_std_init(sstrm, NULL, 0, procs, mode);
    sstrm->procs.process = temp->process;
    state->template = temp;
    state->memory = mem;
    state->min_left = 1;
    state->eof = 0;
    state->proc = *sop;
    make_empty_string(&state->data, a_all);
    state->index = 0;
    sstrm->state = (stream_state *) state;
    *psstrm = sstrm;
    return 0;
}

/* Handle an interrupt during a stream operation. */
/* This is logically unrelated to procedure streams, */
/* but it is also associated with the interpreter stream machinery. */
private int
s_handle_intc(i_ctx_t *i_ctx_p, const ref *pstate, int nstate,
              op_proc_t cont)
{
    int npush = nstate + 2;

    check_estack(npush);
    if (nstate)
        memcpy(esp + 2, pstate, nstate * sizeof(ref));
#if 0                           /* **************** */
    {
        int code = gs_interpret_error(e_interrupt, (ref *) (esp + npush));

        if (code < 0)
            return code;
    }
#else /* **************** */
    npush--;
#endif /* **************** */
    make_op_estack(esp + 1, cont);
    esp += npush;
    return o_push_estack;
}

/* Set default parameter values (actually, just clear pointers). */
private void
s_proc_set_defaults(stream_state * st)
{
    stream_proc_state *const ss = (stream_proc_state *) st;

    make_null(&ss->proc);
    make_null(&ss->data);
}

/* ---------------- Read streams ---------------- */

/* Forward references */
private stream_proc_process(s_proc_read_process);
private int s_proc_read_continue(P1(i_ctx_t *));

/* Stream templates */
private const stream_template s_proc_read_template = {
    &st_sproc_state, NULL, s_proc_read_process, 1, 1,
    NULL, s_proc_set_defaults
};
private const stream_procs s_proc_read_procs = {
    s_std_noavailable, s_std_noseek, s_std_read_reset,
    s_std_read_flush, s_std_null, NULL
};

/* Allocate and open a procedure-based read stream. */
/* The caller must have checked that *sop is a procedure. */
int
sread_proc(ref * sop, stream ** psstrm, gs_ref_memory_t *imem)
{
    int code =
        s_proc_init(sop, psstrm, s_mode_read, &s_proc_read_template,
                    &s_proc_read_procs, imem);

    if (code < 0)
        return code;
    (*psstrm)->end_status = CALLC;
    return code;
}

/* Handle an input request. */
private int
s_proc_read_process(stream_state * st, stream_cursor_read * ignore_pr,
                    stream_cursor_write * pw, bool last)
{
    /* Move data from the string returned by the procedure */
    /* into the stream buffer, or ask for a callback. */
    stream_proc_state *const ss = (stream_proc_state *) st;
    uint count = r_size(&ss->data) - ss->index;

    if (count > 0) {
        uint wcount = pw->limit - pw->ptr;

        if (wcount < count)
            count = wcount;
        memcpy(pw->ptr + 1, ss->data.value.bytes + ss->index, count);
        pw->ptr += count;
        ss->index += count;
        return 1;
    }
    return (ss->eof ? EOFC : CALLC);
}

/* Handle an exception (INTC or CALLC) from a read stream */
/* whose buffer is empty. */
int
s_handle_read_exception(i_ctx_t *i_ctx_p, int status, const ref * fop,
                        const ref * pstate, int nstate, op_proc_t cont)
{
    int npush = nstate + 4;
    stream *ps;

    switch (status) {
        case INTC:
            return s_handle_intc(i_ctx_p, pstate, nstate, cont);
        case CALLC:
            break;
        default:
            return_error(e_ioerror);
    }
    /* Find the stream whose buffer needs refilling. */
    for (ps = fptr(fop); ps->strm != 0;)
        ps = ps->strm;
    check_estack(npush);
    if (nstate)
        memcpy(esp + 2, pstate, nstate * sizeof(ref));
    make_op_estack(esp + 1, cont);
    esp += npush;
    make_op_estack(esp - 2, s_proc_read_continue);
    esp[-1] = *fop;
    r_clear_attrs(esp - 1, a_executable);
    *esp = ((stream_proc_state *) ps->state)->proc;
    return o_push_estack;
}
/* Continue a read operation after returning from a procedure callout. */
/* osp[0] contains the file (pushed on the e-stack by handle_read_status); */
/* osp[-1] contains the new data string (pushed by the procedure). */
/* The top of the e-stack contains the real continuation. */
private int
s_proc_read_continue(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    os_ptr opbuf = op - 1;
    stream *ps;
    stream_proc_state *ss;

    check_file(ps, op);
    check_read_type(*opbuf, t_string);
    while ((ps->end_status = 0, ps->strm) != 0)
        ps = ps->strm;
    ss = (stream_proc_state *) ps->state;
    ss->data = *opbuf;
    ss->index = 0;
    if (r_size(opbuf) == 0)
        ss->eof = true;
    pop(2);
    return 0;
}

/* ---------------- Write streams ---------------- */

/* Forward references */
private stream_proc_flush(s_proc_write_flush);
private stream_proc_process(s_proc_write_process);
private int s_proc_write_continue(P1(i_ctx_t *));

/* Stream templates */
private const stream_template s_proc_write_template = {
    &st_sproc_state, NULL, s_proc_write_process, 1, 1,
    NULL, s_proc_set_defaults
};
private const stream_procs s_proc_write_procs = {
    s_std_noavailable, s_std_noseek, s_std_write_reset,
    s_proc_write_flush, s_std_null, NULL
};

/* Allocate and open a procedure-based write stream. */
/* The caller must have checked that *sop is a procedure. */
int
swrite_proc(ref * sop, stream ** psstrm, gs_ref_memory_t *imem)
{
    return s_proc_init(sop, psstrm, s_mode_write, &s_proc_write_template,
                       &s_proc_write_procs, imem);
}

/* Handle an output request. */
private int
s_proc_write_process(stream_state * st, stream_cursor_read * pr,
                     stream_cursor_write * ignore_pw, bool last)
{
    /* Move data from the stream buffer to the string */
    /* returned by the procedure, or ask for a callback. */
    stream_proc_state *const ss = (stream_proc_state *) st;
    uint rcount = pr->limit - pr->ptr;

    if (rcount > 0) {
        uint wcount = r_size(&ss->data) - ss->index;
        uint count = min(rcount, wcount);

        memcpy(ss->data.value.bytes + ss->index, pr->ptr + 1, count);
        pr->ptr += count;
        ss->index += count;
        if (rcount > wcount)
            return CALLC;
        else if (last) {
            ss->eof = true;
            return CALLC;
        } else
            return 0;
    }
    return ((ss->eof = last) ? EOFC : 0);
}

/* Flush the output.  This is non-standard because it must call the */
/* procedure. */
private int
s_proc_write_flush(stream *s)
{
    int result = s_process_write_buf(s, false);
    stream_proc_state *const ss = (stream_proc_state *)s->state;

    return (result < 0 || ss->index == 0 ? result : CALLC);
}

/* Handle an exception (INTC or CALLC) from a write stream */
/* whose buffer is full. */
int
s_handle_write_exception(i_ctx_t *i_ctx_p, int status, const ref * fop,
                         const ref * pstate, int nstate, op_proc_t cont)
{
    stream *ps;
    stream_proc_state *psst;

    switch (status) {
        case INTC:
            return s_handle_intc(i_ctx_p, pstate, nstate, cont);
        case CALLC:
            break;
        default:
            return_error(e_ioerror);
    }
    /* Find the stream whose buffer needs emptying. */
    for (ps = fptr(fop); ps->strm != 0;)
        ps = ps->strm;
    psst = (stream_proc_state *) ps->state;
    {
        int npush = nstate + 6;

        check_estack(npush);
        if (nstate)
            memcpy(esp + 2, pstate, nstate * sizeof(ref));
        make_op_estack(esp + 1, cont);
        esp += npush;
        make_op_estack(esp - 4, s_proc_write_continue);
        esp[-3] = *fop;
        r_clear_attrs(esp - 3, a_executable);
        make_bool(esp - 1, !psst->eof);
    }
    esp[-2] = psst->proc;
    *esp = psst->data;
    r_set_size(esp, psst->index);
    return o_push_estack;
}
/* Continue a write operation after returning from a procedure callout. */
/* osp[0] contains the file (pushed on the e-stack by handle_write_status); */
/* osp[-1] contains the new buffer string (pushed by the procedure). */
/* The top of the e-stack contains the real continuation. */
private int
s_proc_write_continue(i_ctx_t *i_ctx_p)
{
    os_ptr op = osp;
    os_ptr opbuf = op - 1;
    stream *ps;
    stream_proc_state *ss;

    check_file(ps, op);
    check_write_type(*opbuf, t_string);
    while (ps->strm != 0) {
	if (ps->end_status == CALLC)
	    ps->end_status = 0;
	ps = ps->strm;
    }
    ps->end_status = 0;
    ss = (stream_proc_state *) ps->state;
    ss->data = *opbuf;
    ss->index = 0;
    pop(2);
    return 0;
}

/* ------ More generic ------ */

/* Test whether a stream is procedure-based. */
bool
s_is_proc(const stream *s)
{
    return (s->procs.process == s_proc_read_process ||
            s->procs.process == s_proc_write_process);
}

/* ------ Initialization procedure ------ */

const op_def zfproc_op_defs[] =
{
                /* Internal operators */
    {"2%s_proc_read_continue", s_proc_read_continue},
    {"2%s_proc_write_continue", s_proc_write_continue},
    op_def_end(0)
};
