aboutsummaryrefslogtreecommitdiffstats
path: root/sexpr.c
blob: 7e5644ce4e751f6d56c6f2f7725bece197d0d317 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define DEFAULT "(& (>> t 6) (& (* 2 t) (>> t 1)))"
# define NUMNODE 160

struct node {
    char type;
    char cval;
    unsigned int ival;
    struct node *lval;
    struct node *rval;
};

void print_sexpr(struct node *sexpr);
unsigned int execute(struct node *sexpr, unsigned int t);
void play(struct node *sexpr);
int find_split(char* s, int start, int end);
struct node *parse(char *s, int start, int end);
struct node *new_node(char type, char cval, unsigned int ival,
                      struct node *lval, struct node *rval);
void test();

static struct node node_table[NUMNODE];
static int newest_node = 0;

char inbuffer[256];

int sstrlen(char *s, int max);

int sstrlen(char *s, int max) {
    int i;
    for (i=0; i<max; i++) {
        if (s[i] == '\n' || s[i] == '\0') {
            return i+1;
        }
    }
    return max;
}

void main() {
    int len;
    //test();
    if (stderr == stdout) {
        printf("You are expected to send stderr and stdout different ways.\n");
        exit(-1);
    }
    while (1) {
        fprintf(stderr, "Input a tune in exact s-expr syntax:\n");
        fprintf(stderr, "> ");
        fgets(inbuffer, 256, stdin);    
        len = sstrlen(inbuffer, 256);
        if (len == 256 || len < 1)
            fprintf(stderr, "Invalid input!\n");
        else
            break;
    }
    play(parse(inbuffer, 0, len-2));
    //play(parse(DEFAULT, 0, strlen(DEFAULT)-1));
};

void test() {
    printf(DEFAULT);
    printf("\n");
    print_sexpr(parse(DEFAULT, 0, strlen(DEFAULT)-1));
    printf("\n");
}

int digtoi(char *s, int start, int end) {
    int num = 0;
    for(;start<=end;start++) {
        if (! isdigit(s[start])) {
            fprintf(stderr, "parse: not a digit: %c", s[start]);
            exit(-1);
        }
        num = num*10 + (s[start] - '0');
    }
    return num;
}

struct node *parse(char *s, int start, int end) {
    struct node *lval, *rval;
    char cval;
    int offset, split;

    // number
    if (isdigit(s[start])) {
        return new_node('n', '_', digtoi(s, start, end), NULL, NULL);
    }
    // variable
    if ((s[start] == 't') && (end-start == 0)) {
        return new_node('v', '_', 0, NULL, NULL);
    }

    // must be an s-exp
    if ( !(s[start] == '(' && s[end] == ')') || (end-start < 4)) {
        fprintf(stderr, "parse: unparsable: ");
        for (;start<=end;start++) {
            fprintf(stderr, "%c", s[start]);
        }
        fprintf(stderr, "\n");
        exit(-1);
    }

    // unitary operator
    if (s[start+1] == '~') {
        rval = parse(s, start+3, end-1);
        return new_node('u', '~', 0, NULL, rval);
    }

    // various binary operators
    if ( strchr("*/%+-&^|<>%", s[start+1]) != NULL) {
        cval = s[start+1];
        offset = 3;
        if (cval == '<' && s[start+2] == '<' && s[start+3] == ' ') {
            cval = 'l';
            offset = 4;
        } else if (cval == '>' && s[start+2] == '>' && s[start+3] == ' ') {
            cval = 'r';
            offset = 4;
        } else if (s[start+2] != ' ') {
            fprintf(stderr, "parse: invalid operator: %c\n", cval);
            exit(-1);
        }
        split = find_split(s, start+offset, end-1);
        lval = parse(s, start+offset, split-1);
        rval = parse(s, split+1, end-1);
        return new_node('b', cval, 0, lval, rval);
    }

    // should not get here 
    fprintf(stderr, "parse: feel through\n");
    exit(-1);
}

unsigned int execute(struct node *sexpr, unsigned int t) {
    switch (sexpr->type) {
    // atom
    case 'v':
        return t;
    case 'n':
        return sexpr->ival;
    // unary
    case 'u':
        if (sexpr->cval == '~') {
            return (~ execute(sexpr->rval, t));
        } else {
            fprintf(stderr, "unexpected unary oper: %c",  sexpr->cval);
        }
    // binary
    case 'b':
        switch (sexpr->cval) {
        case '+':
            return execute(sexpr->lval, t) + execute(sexpr->rval, t);
        case '-':
            return execute(sexpr->lval, t) - execute(sexpr->rval, t);
        case '*':
            return execute(sexpr->lval, t) * execute(sexpr->rval, t);
        case '/':
            return execute(sexpr->lval, t) / execute(sexpr->rval, t);
        case '^':
            return execute(sexpr->lval, t) ^ execute(sexpr->rval, t);
        case '&':
            return execute(sexpr->lval, t) & execute(sexpr->rval, t);
        case '|':
            return execute(sexpr->lval, t) | execute(sexpr->rval, t);
        case '%':
            return execute(sexpr->lval, t) % execute(sexpr->rval, t);
        case 'r':
            return execute(sexpr->lval, t) >> execute(sexpr->rval, t);
        case 'l':
            return execute(sexpr->lval, t) << execute(sexpr->rval, t);
        default:
            fprintf(stderr, "unexpected binary oper: %c", sexpr->cval);
            exit(-1);
        }
    default:
        fprintf(stderr, "execute: unknown type: %c", sexpr->type);
        exit(-1);
    }
}

void play(struct node *sexpr) {
    unsigned int t = 0;
    for (;;t++) {
        printf("%c", (char)(0x000000FF & execute(sexpr, t)));
    }
    return;
}

int find_split(char *s, int start, int end) {
    int depth = 0;
    int i;
    for (i=start; i <= end; i++) {
        if ((depth == 0) && (s[i] == ' '))
            return i;
        if (s[i] == '(')
            depth++;
        if (s[i] == ')')
            depth--; 
        if (depth < 0) {
            fprintf(stderr, "parse: unmatched ')'\n");
            exit(-1);
        }
    }
    if (depth > 0) {
        fprintf(stderr, "parse: unmatched '('\n");
        exit(-1);
    }
    fprintf(stderr, "parse: could not find split\n");
    exit(-1);
}

void print_sexpr(struct node *sexpr) {
    char oper = '_';
    char twice = 0;
    switch (sexpr->type) {
    // atoms
    case 'v':
        printf("t");
        break;
    case 'n':
        printf("%d", sexpr->ival);
        break;
    // unary operators
    case 'u':
        if (sexpr->cval == '~') {
            printf("(~ ");
            print_sexpr(sexpr->rval);
            printf(")");
        } else {
            fprintf(stderr, "unexpected unary: %c", sexpr->cval);
        }
    // binary operators
    case 'b':
        if ((sexpr->cval == 'l') || (sexpr->cval == 'r')) {
            twice = 1;
            oper = '<';
            if (sexpr->cval == 'r')
                oper = '>';
        } else {
            oper = sexpr->cval;
        }
        if (strchr("+-*/^|&<>", oper) != NULL) {
            printf("(%c ", oper);
            if (twice)
                printf("%c", oper);
            print_sexpr(sexpr->lval);
            printf(" ");
            print_sexpr(sexpr->rval);
            printf(")");
        } else {
            fprintf(stderr, "unexpected binary: %c", sexpr->cval);
            exit(-1);
        }

    }
}

struct node *new_node(char type, char cval, unsigned int ival, 
                      struct node *lval, struct node *rval) {
    struct node *n;
    newest_node++;
    if (newest_node >= NUMNODE) {
        fprintf(stderr, "node table overrun\n");
        exit(-1);
    }
    n = &node_table[newest_node];
    n->type = type;
    n->cval = cval;
    n->ival = ival;
    n->lval = lval;
    n->rval = rval;
    return n;
}