source: branches/blt4/packages/vizservers/vtkvis/CmdProc.cpp @ 2542

/* -*- mode: c++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 * Copyright (C) 2011, Purdue Research Foundation
 *
 * Author: George A. Howlett <gah@purdue.edu>
 */

#include <cstring>
#include <tcl.h>

#include "CmdProc.h"

using namespace Rappture;

/**
 * Performs a binary search on the array of command operation
 * specifications to find a partial, anchored match for the given
 * operation string.
 *
 * \return If the string matches unambiguously the index of the specification in
 * the array is returned.  If the string does not match, even as an
 * abbreviation, any operation, -1 is returned.  If the string matches,
 * but ambiguously -2 is returned.
 */
static int
BinaryOpSearch(CmdSpec *specs, 
               int nSpecs, 
               char *string)       /* Name of minor operation to search for */
{
    char c;
    int high, low;
    size_t length;

    low = 0;
    high = nSpecs - 1;
    c = string[0];
    length = strlen(string);
    while (low <= high) {
        CmdSpec *specPtr;
        int compare;
        int median;
    
        median = (low + high) >> 1;
        specPtr = specs + median;

        /* Test the first character */
        compare = c - specPtr->name[0];
        if (compare == 0) {
            /* Now test the entire string */
            compare = strncmp(string, specPtr->name, length);
            if (compare == 0) {
                if ((int)length < specPtr->minChars) {
                    return -2;  /* Ambiguous operation name */
                }
            }
        }
        if (compare < 0) {
            high = median - 1;
        } else if (compare > 0) {
            low = median + 1;
        } else {
            return median;  /* Op found. */
        }
    }
    return -1;          /* Can't find operation */
}


/**
 * Performs a binary search on the array of command operation
 * specifications to find a partial, anchored match for the given
 * operation string.
 *
 * \return If the string matches unambiguously the index of the specification in
 * the array is returned.  If the string does not match, even as an
 * abbreviation, any operation, -1 is returned.  If the string matches,
 * but ambiguously -2 is returned.
 */
static int
LinearOpSearch(CmdSpec *specs,
               int nSpecs,
               char *string)       /* Name of minor operation to search for */
{
    CmdSpec *specPtr;
    char c;
    size_t length;
    int nMatches, last;
    int i;

    c = string[0];
    length = strlen(string);
    nMatches = 0;
    last = -1;
    for (specPtr = specs, i = 0; i < nSpecs; i++, specPtr++) {
        if ((c == specPtr->name[0]) && 
            (strncmp(string, specPtr->name, length) == 0)) {
            last = i;
            nMatches++;
            if ((int)length == specPtr->minChars) {
                break;
            }
        }
    }
    if (nMatches > 1) {
        return -2;      /* Ambiguous operation name */
    } 
    if (nMatches == 0) {
        return -1;      /* Can't find operation */
    } 
    return last;        /* Op found. */
}

/**
 * \brief Find the command operation given a string name.
 * 
 * This is useful where a group of command operations have the same argument 
 * signature.
 *
 * \return If found, a pointer to the procedure (function pointer) is returned.
 * Otherwise NULL is returned and an error message containing a list of
 * the possible commands is returned in interp->result.
 */
Tcl_ObjCmdProc *
Rappture::GetOpFromObj(Tcl_Interp *interp,      /* Interpreter to report errors to */
                       int nSpecs,              /* Number of specifications in array */
                       CmdSpec *specs,          /* Op specification array */
                       int operPos,             /* Position of operation in argument
                                                 * list. */
                       int objc,                /* Number of arguments in the argument
                                                 * vector.  This includes any prefixed
                                                 * arguments */ 
                       Tcl_Obj *const *objv,    /* Argument vector */
                       int flags)
{
    CmdSpec *specPtr;
    char *string;
    int n;

    if (objc <= operPos) {  /* No operation argument */
        Tcl_AppendResult(interp, "wrong # args: ", (char *)NULL);
usage:
        Tcl_AppendResult(interp, "should be one of...", (char *)NULL);
        for (n = 0; n < nSpecs; n++) {
            int i;

            Tcl_AppendResult(interp, "\n  ", (char *)NULL);
            for (i = 0; i < operPos; i++) {
                Tcl_AppendResult(interp, Tcl_GetString(objv[i]), " ", 
                                 (char *)NULL);
            }
            specPtr = specs + n;
            Tcl_AppendResult(interp, specPtr->name, " ", specPtr->usage,
                             (char *)NULL);
        }
        return NULL;
    }
    string = Tcl_GetString(objv[operPos]);
    if (flags & CMDSPEC_LINEAR_SEARCH) {
        n = LinearOpSearch(specs, nSpecs, string);
    } else {
        n = BinaryOpSearch(specs, nSpecs, string);
    }
    if (n == -2) {
        char c;
        size_t length;

        Tcl_AppendResult(interp, "ambiguous", (char *)NULL);
        if (operPos > 2) {
            Tcl_AppendResult(interp, " ", Tcl_GetString(objv[operPos - 1]), 
                             (char *)NULL);
        }
        Tcl_AppendResult(interp, " operation \"", string, "\" matches: ",
                         (char *)NULL);

        c = string[0];
        length = strlen(string);
        for (n = 0; n < nSpecs; n++) {
            specPtr = specs + n;
            if ((c == specPtr->name[0]) &&
                (strncmp(string, specPtr->name, length) == 0)) {
                Tcl_AppendResult(interp, " ", specPtr->name, (char *)NULL);
            }
        }
        return NULL;

    } else if (n == -1) {   /* Can't find operation, display help */
        Tcl_AppendResult(interp, "bad", (char *)NULL);
        if (operPos > 2) {
            Tcl_AppendResult(interp, " ", Tcl_GetString(objv[operPos - 1]), 
                             (char *)NULL);
        }
        Tcl_AppendResult(interp, " operation \"", string, "\": ", (char *)NULL);
        goto usage;
    }
    specPtr = specs + n;
    if ((objc < specPtr->minArgs) || 
        ((specPtr->maxArgs > 0) && (objc > specPtr->maxArgs))) {
        int i;

        Tcl_AppendResult(interp, "wrong # args: should be \"", (char *)NULL);
        for (i = 0; i < operPos; i++) {
            Tcl_AppendResult(interp, Tcl_GetString(objv[i]), " ", 
                             (char *)NULL);
        }
        Tcl_AppendResult(interp, specPtr->name, " ", specPtr->usage, "\"",
                         (char *)NULL);
        return NULL;
    }
    return specPtr->proc;
}