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Merge pull request #4 from aleamb/parser-refactor
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Parser refactor
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@aleamb
aleamb authored Jun 7, 2020
2 parents 9587633 + fb9ccb8 commit 0d6b997
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Showing 4 changed files with 69 additions and 124 deletions.
12 changes: 0 additions & 12 deletions init.lisp
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2 changes: 1 addition & 1 deletion memory.c
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ typedef struct _list {
struct _list* next;
} SEXPLIST;

SEXPLIST sexplist = { 0 };
SEXPLIST sexplist = { NULL, NULL };
SEXPLIST* sexplist_ptr = &sexplist;

void* s_exp_alloc(int size) {
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172 changes: 66 additions & 106 deletions parser.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,139 +28,99 @@
#include "parser.h"

const char* atom_chars = ".?_-\\/¿!¡=&$@~¬+-*~<>%";
const char* ignored_chars = " \n\t\r";

S_EXP s_expression(S_EXP_PARSER_CONTEXT* lexer);
S_EXP s_list(S_EXP_PARSER_CONTEXT* lexer);

static int atom_valid_char( char c) {
static int atom_valid_char(char c) {
return isalnum(c) || strchr(atom_chars, c) != NULL;
}

static int is_ignore_char(char c) {
return strchr(ignored_chars, c) != NULL;
}

static void lexer_init(S_EXP_PARSER_CONTEXT* context, FILE* stream) {
context->stream = stream;
memset(context->buffer, 0, sizeof(context->buffer));
context->buffer_index = 0;
context->line = 1;
context->position = 0;
context->status = 0;
memset(context->token_value, 0, ATOM_SIZE);
}

TOKEN next_token(S_EXP_PARSER_CONTEXT* context, int peek) {

char c = '\0';
int ti = 0;
int token_available = 0;
int prior_buffer_pos = context->buffer_index;
context->status = 0;
while (!token_available) {
if (!(context->buffer[context->buffer_index])) {
fgets(context->buffer, EXPR_SIZE, context->stream);
if (feof(context->stream)) {
context->status = 1;
return context->token;
}
context->status = 0;
context->buffer_index = 0;
prior_buffer_pos = 0;
}
c = context->buffer[context->buffer_index++];
if (!peek) context->position++;
if (c != '\n' && c != '\t' && c != ' ' && c != '\r') {
switch (c) {
case '(':
if (ti > 0) {
context->token = TOKEN_ATOM;
context->buffer_index -= 1;
} else {
context->token = TOKEN_LIST_OPEN;
}
token_available = 1;
break;
case ')':
if (ti > 0) {
context->token = TOKEN_ATOM;
context->buffer_index -= 1;
} else {
context->token = TOKEN_LIST_CLOSE;
}
token_available = 1;
break;
case '\'':
if (ti > 0) {
context->token = TOKEN_ATOM;
context->buffer_index -= 1;
} else {
context->token = TOKEN_QUOTE;
}
token_available = 1;
break;
default:
if (atom_valid_char(c)) {
context->token_value[ti++] = c;
} else {
fprintf(stderr, "Not valid atom character %c at position %d in line %d\n", c, context->position, context->line);
return context->token;
}
}
} else {
if (ti > 0) {
context->token = TOKEN_ATOM;
token_available = 1;
}
}
if (c == '\n') {
context->line++;
context->position = 0;
}
}
context->token_value[ti] = 0;
if (peek) {
context->buffer_index = prior_buffer_pos;
}
return context->token;
}

TOKEN peek_token(S_EXP_PARSER_CONTEXT* context) {
return next_token(context, 1);
context->line = 0;
}

S_EXP s_list(S_EXP_PARSER_CONTEXT* context) {
S_EXP current = NULL;
S_EXP list = NULL;
TOKEN token;
while ((token = peek_token(context)) != TOKEN_LIST_CLOSE) {
S_EXP expr = s_exp_create_cons(s_expression(context), NULL);
if (current != NULL) {
s_exp_set_cdr(current, expr);
} else {
list = expr;
}
current = expr;
static char lexer_getchar(S_EXP_PARSER_CONTEXT* context) {
if (context->buffer[context->buffer_index] == 0) {
memset(context->token_value, 0, ATOM_SIZE);
if (!fgets(context->buffer, EXPR_SIZE, context->stream))
return EOF;
context->buffer_index = 0;
context->position = 0;
context->line++;
}
next_token(context, 0);

return list ? list : s_exp_create_cons(NULL, NULL);
context->position++;
return context->buffer[context->buffer_index++];
}

S_EXP s_expression(S_EXP_PARSER_CONTEXT* context) {
TOKEN token = next_token(context, 0);
if (context->status)
return NULL;
static S_EXP s_expression_analyze(S_EXP_PARSER_CONTEXT* context, TOKEN token) {
S_EXP sexp = NULL;
if (token == TOKEN_LIST_OPEN) {
if (token == TOKEN_EOF) return NULL;
if (token == TOKEN_INVALID) {
fprintf(stderr, "Lexical error at line %d, position %d - Token %s not expected\n", context->line, context->position, context->token_value);
} else if (token == TOKEN_LIST_OPEN) {
sexp = s_list(context);
} else if (token == TOKEN_QUOTE) {
sexp = s_expression(context);
sexp = s_exp_create_cons(s_exp_create_atom("quote"), s_exp_create_cons(sexp, NULL));
} else if (token == TOKEN_ATOM) {
sexp = s_exp_create_atom(context->token_value);
} else {
fprintf(stderr, "Syntax error in line %d, position %d\n", context->line, context->buffer_index);
return NULL;
fprintf(stderr, "Syntax error at line %d, position %d\n", context->line, context->position);
}
return sexp;
}

TOKEN next_token(S_EXP_PARSER_CONTEXT* context) {
char c = 0;
while (is_ignore_char( (c = lexer_getchar(context)) ));
if (atom_valid_char(c)) {
int n = 0;
do {
context->token_value[n++] = c;
c = lexer_getchar(context);
} while(atom_valid_char(c));
context->token_value[n] = 0;
context->buffer_index--;
context->token = TOKEN_ATOM;
} else {
if (c == '\'') context->token = TOKEN_QUOTE;
else if (c == '(') context->token = TOKEN_LIST_OPEN;
else if (c == ')') context->token = TOKEN_LIST_CLOSE;
else if (c == EOF) context->token = TOKEN_EOF;
else {
context->token_value[0] = c;
context->token = TOKEN_INVALID;
}
}
return context->token;
}

S_EXP s_list(S_EXP_PARSER_CONTEXT* context) {
TOKEN token = next_token(context);
if (token == TOKEN_EOF) {
fprintf(stderr, "EOF found at line %d, position %d\n", context->line, context->position);
return NULL;
}
if (token == TOKEN_LIST_CLOSE) return NULL;
S_EXP car = s_expression_analyze(context, token);
S_EXP cdr = s_list(context);
return s_exp_create_cons(car, cdr);
}

S_EXP s_expression(S_EXP_PARSER_CONTEXT* context) {
TOKEN token = next_token(context);
return s_expression_analyze(context, token);
}

S_EXP parse(S_EXP_PARSER_CONTEXT* context) {
S_EXP result = NULL;
result = s_expression(context);
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7 changes: 2 additions & 5 deletions parser.h
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Original file line number Diff line number Diff line change
Expand Up @@ -31,13 +31,13 @@
#define EXPR_SIZE 512
#define ATOM_SIZE 64


typedef enum {
TOKEN_LIST_OPEN,
TOKEN_LIST_CLOSE,
TOKEN_QUOTE,
TOKEN_ATOM,
NO_TOKEN
TOKEN_INVALID,
TOKEN_EOF
} TOKEN;

typedef struct {
Expand All @@ -47,13 +47,10 @@ typedef struct {
int buffer_index;
int line;
int position;
int status;
TOKEN token;
} S_EXP_PARSER_CONTEXT;


S_EXP parse(S_EXP_PARSER_CONTEXT*);
S_EXP_PARSER_CONTEXT* init_parser(FILE* stream);


#endif /* _PARSER_H_ */

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