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      1 /* -*- c++ -*- */
      2 /*
      3  * Copyright  2010 Intel Corporation
      4  *
      5  * Permission is hereby granted, free of charge, to any person obtaining a
      6  * copy of this software and associated documentation files (the "Software"),
      7  * to deal in the Software without restriction, including without limitation
      8  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
      9  * and/or sell copies of the Software, and to permit persons to whom the
     10  * Software is furnished to do so, subject to the following conditions:
     11  *
     12  * The above copyright notice and this permission notice (including the next
     13  * paragraph) shall be included in all copies or substantial portions of the
     14  * Software.
     15  *
     16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
     19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     21  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     22  * DEALINGS IN THE SOFTWARE.
     23  */
     24 
     25 #include <assert.h>
     26 #include <stdio.h>
     27 #include <math.h>
     28 #include "s_expression.h"
     29 
     30 s_symbol::s_symbol(const char *str, size_t n)
     31 {
     32    /* Assume the given string is already nul-terminated and in memory that
     33     * will live as long as this node.
     34     */
     35    assert(str[n] == '\0');
     36    this->str = str;
     37 }
     38 
     39 s_list::s_list()
     40 {
     41 }
     42 
     43 static void
     44 skip_whitespace(const char *&src, char *&symbol_buffer)
     45 {
     46    size_t n = strspn(src, " \v\t\r\n");
     47    src += n;
     48    symbol_buffer += n;
     49    /* Also skip Scheme-style comments: semi-colon 'til end of line */
     50    if (src[0] == ';') {
     51       n = strcspn(src, "\n");
     52       src += n;
     53       symbol_buffer += n;
     54       skip_whitespace(src, symbol_buffer);
     55    }
     56 }
     57 
     58 static s_expression *
     59 read_atom(void *ctx, const char *&src, char *&symbol_buffer)
     60 {
     61    s_expression *expr = NULL;
     62 
     63    skip_whitespace(src, symbol_buffer);
     64 
     65    size_t n = strcspn(src, "( \v\t\r\n);");
     66    if (n == 0)
     67       return NULL; // no atom
     68 
     69    // Check for the special symbol '+INF', which means +Infinity.  Note: C99
     70    // requires strtof to parse '+INF' as +Infinity, but we still support some
     71    // non-C99-compliant compilers (e.g. MSVC).
     72    if (n == 4 && strncmp(src, "+INF", 4) == 0) {
     73       expr = new(ctx) s_float(INFINITY);
     74    } else {
     75       // Check if the atom is a number.
     76       char *float_end = NULL;
     77       float f = _mesa_strtof(src, &float_end);
     78       if (float_end != src) {
     79          char *int_end = NULL;
     80          int i = strtol(src, &int_end, 10);
     81          // If strtof matched more characters, it must have a decimal part
     82          if (float_end > int_end)
     83             expr = new(ctx) s_float(f);
     84          else
     85             expr = new(ctx) s_int(i);
     86       } else {
     87          // Not a number; return a symbol.
     88          symbol_buffer[n] = '\0';
     89          expr = new(ctx) s_symbol(symbol_buffer, n);
     90       }
     91    }
     92 
     93    src += n;
     94    symbol_buffer += n;
     95 
     96    return expr;
     97 }
     98 
     99 static s_expression *
    100 __read_expression(void *ctx, const char *&src, char *&symbol_buffer)
    101 {
    102    s_expression *atom = read_atom(ctx, src, symbol_buffer);
    103    if (atom != NULL)
    104       return atom;
    105 
    106    skip_whitespace(src, symbol_buffer);
    107    if (src[0] == '(') {
    108       ++src;
    109       ++symbol_buffer;
    110 
    111       s_list *list = new(ctx) s_list;
    112       s_expression *expr;
    113 
    114       while ((expr = __read_expression(ctx, src, symbol_buffer)) != NULL) {
    115 	 list->subexpressions.push_tail(expr);
    116       }
    117       skip_whitespace(src, symbol_buffer);
    118       if (src[0] != ')') {
    119 	 printf("Unclosed expression (check your parenthesis).\n");
    120 	 return NULL;
    121       }
    122       ++src;
    123       ++symbol_buffer;
    124       return list;
    125    }
    126    return NULL;
    127 }
    128 
    129 s_expression *
    130 s_expression::read_expression(void *ctx, const char *&src)
    131 {
    132    assert(src != NULL);
    133 
    134    /* When we encounter a Symbol, we need to save a nul-terminated copy of
    135     * the string.  However, ralloc_strndup'ing every individual Symbol is
    136     * extremely expensive.  We could avoid this by simply overwriting the
    137     * next character (guaranteed to be whitespace, parens, or semicolon) with
    138     * a nul-byte.  But overwriting non-whitespace would mess up parsing.
    139     *
    140     * So, just copy the whole buffer ahead of time.  Walk both, leaving the
    141     * original source string unmodified, and altering the copy to contain the
    142     * necessary nul-bytes whenever we encounter a symbol.
    143     */
    144    char *symbol_buffer = ralloc_strdup(ctx, src);
    145    return __read_expression(ctx, src, symbol_buffer);
    146 }
    147 
    148 void s_int::print()
    149 {
    150    printf("%d", this->val);
    151 }
    152 
    153 void s_float::print()
    154 {
    155    printf("%f", this->val);
    156 }
    157 
    158 void s_symbol::print()
    159 {
    160    printf("%s", this->str);
    161 }
    162 
    163 void s_list::print()
    164 {
    165    printf("(");
    166    foreach_in_list(s_expression, expr, &this->subexpressions) {
    167       expr->print();
    168       if (!expr->next->is_tail_sentinel())
    169 	 printf(" ");
    170    }
    171    printf(")");
    172 }
    173 
    174 // --------------------------------------------------
    175 
    176 bool
    177 s_pattern::match(s_expression *expr)
    178 {
    179    switch (type)
    180    {
    181    case EXPR:   *p_expr = expr; break;
    182    case LIST:   if (expr->is_list())   *p_list   = (s_list *)   expr; break;
    183    case SYMBOL: if (expr->is_symbol()) *p_symbol = (s_symbol *) expr; break;
    184    case NUMBER: if (expr->is_number()) *p_number = (s_number *) expr; break;
    185    case INT:    if (expr->is_int())    *p_int    = (s_int *)    expr; break;
    186    case STRING:
    187       s_symbol *sym = SX_AS_SYMBOL(expr);
    188       if (sym != NULL && strcmp(sym->value(), literal) == 0)
    189 	 return true;
    190       return false;
    191    };
    192 
    193    return *p_expr == expr;
    194 }
    195 
    196 bool
    197 s_match(s_expression *top, unsigned n, s_pattern *pattern, bool partial)
    198 {
    199    s_list *list = SX_AS_LIST(top);
    200    if (list == NULL)
    201       return false;
    202 
    203    unsigned i = 0;
    204    foreach_in_list(s_expression, expr, &list->subexpressions) {
    205       if (i >= n)
    206 	 return partial; /* More actual items than the pattern expected */
    207 
    208       if (expr == NULL || !pattern[i].match(expr))
    209 	 return false;
    210 
    211       i++;
    212    }
    213 
    214    if (i < n)
    215       return false; /* Less actual items than the pattern expected */
    216 
    217    return true;
    218 }
    219