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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdbool.h>
typedef int stackitem;
typedef struct {
int size;
int maxsize;
stackitem* start;
} stack;
stack* newstack() {
stack* s = malloc(sizeof(stack));
s->size = 0;
s->maxsize = 1024;
s->start = malloc(sizeof(stackitem) * s->maxsize);
return s;
}
stackitem pop(stack* s) {
if (s->size > 0) {
s->size = s->size - 1;
stackitem si = s->start[s->size];
return si;
} else {
// tried to pop empty stack
return 0;
}
}
stackitem peek(stack* s) {
if (s->size > 0) {
return s->start[s->size - 1];
} else {
// tried to pop empty stack
return 0;
}
}
void dump(stack* s) {
for (int i = 0; i < s->size; i++) {
printf("%d,", s->start[i]);
}
printf("\n");
}
void push(stack *s, stackitem si) {
// fprintf(stderr, "pushing %d", si);
if (s->size >= s->maxsize) {
fprintf(stderr, "Error Stack Overflow");
exit(1);
} else {
s->start[s->size] = si;
s->size = s->size + 1;
}
}
void add(stack *s) {
int x = pop(s);
int y = pop(s);
// fprintf(stderr, "adding %d + %d",x,y);
push(s, x + y);
}
void sub(stack *s) {
int x = pop(s);
int y = pop(s);
push(s, y - x);
}
void s_dup(stack *s) {
int x = pop(s);
push(s, x);
push(s, x);
}
typedef void (*stackop)(stack *);
typedef struct {
char* word;
bool isscript;
union {
stackop op;
struct {
char* script;
int scriptlen;
};
};
} wordop;
#define OPTABLE_MAX_SIZE 1024
wordop optable[OPTABLE_MAX_SIZE] = {
{"+", false, add},
{"-", false, sub},
{"dup", false, s_dup},
{"dump", false, dump},
};
int optablelen = 4;
const int DEFINED_FUNC_MAX_LENGTH = 1024;
const int WORD_LEN_LIMIT = 255;
int defineop(int starti, char *input) {
// code to be evaluated when function is called
char *funcscript = malloc(sizeof(char) * DEFINED_FUNC_MAX_LENGTH);
int funcscripti = 0;
// name by which the function will be called
char *opcode = malloc(sizeof(char) * WORD_LEN_LIMIT);
int opcodei = 0;
// skip ' ' and ':'
while (input[starti] == ' ' || input[starti] == ':') {
starti++;
}
// get name
while (input[starti] != ' ' && opcodei < WORD_LEN_LIMIT) {
opcode[opcodei++] = input[starti++];
}
opcode[opcodei] = '\0';
// get code
while (input[starti] != ';' && funcscripti < DEFINED_FUNC_MAX_LENGTH) {
funcscript[funcscripti++] = input[starti++];
}
funcscript[funcscripti] = '\0';
if (optablelen >= OPTABLE_MAX_SIZE) {
// Error
fprintf(stderr, "Error: optable reached max size, failed to create new user defined operation");
exit(1);
}
// add op to end of table, and increment size
optable[optablelen].word = opcode; //{opcode, true, funcscript};
optable[optablelen].isscript = true;
optable[optablelen].script = funcscript;
optable[optablelen].scriptlen = funcscripti;
optablelen++;
return starti;
}
wordop* getop(char *word) {
for (int i = 0; i < optablelen; i++) {
if (!strcmp(optable[i].word, word)) {
return &optable[i];
}
}
return 0;
}
//https://stackoverflow.com/a/58585995
char isnumber(char *text) {
int j;
j = strlen(text);
while(j--) {
if(text[j] >= '0' && text[j] <= '9')
continue;
return 0;
}
return 1;
}
void eval(stack* s, int len, char* line);
void exec(stack *s, char *word) {
if (!strcmp(word, "pop") || !strcmp(word, ".")) {
printf("%d\n", pop(s));
return;
} else if (!strcmp(word, "peek")) {
printf("%d\n", peek(s));
return;
}
wordop* op = getop(word);
if (op) {
if (op->isscript) {
eval(s, op->scriptlen, op->script);
} else {
op->op(s);
}
return;
}
if (isnumber(word)) {
push(s, atoi(word));
return;
}
}
void eval(stack* s, int len, char* line) {
char word[WORD_LEN_LIMIT];
int wordi = 0;
for (int i = 0; i < len; i++) {
// end of input is \n, char after end of input is \0
if (line[i] == '\0') {
return;
}
if (line[i] != ' ' &&
line[i] != '\n' && wordi < WORD_LEN_LIMIT - 1) {
if (line[i] == ':') {
i = defineop(i, line);
wordi = 0;
} else {
word[wordi++] = line[i];
}
} else { // end of word
if (wordi > 0) { // don't exec an empty string
word[wordi] = '\0';
exec(s, word);
}
// start new word
wordi = 0;
}
}
}
int main(int argc, char** argv) {
stack* s = newstack();
char *line = NULL;
size_t len = 0;
ssize_t read;
while ((read = getline(&line, &len, stdin)) != -1) {
eval(s, len, line);
}
}
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