gri3-wm/src/commands_parser.c

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/*
* vim:ts=4:sw=4:expandtab
*
* i3 - an improved dynamic tiling window manager
* © 2009-2012 Michael Stapelberg and contributors (see also: LICENSE)
*
* commands_parser.c: hand-written parser to parse commands (commands are what
* you bind on keys and what you can send to i3 using the IPC interface, like
* 'move left' or 'workspace 4').
*
* We use a hand-written parser instead of lex/yacc because our commands are
* easy for humans, not for computers. Thus, its quite hard to specify a
* context-free grammar for the commands. A PEG grammar would be easier, but
* theres downsides to every PEG parser generator I have come accross so far.
*
* This parser is basically a state machine which looks for literals or strings
* and can push either on a stack. After identifying a literal or string, it
* will either transition to the current state, to a different state, or call a
* function (like cmd_move()).
*
* Special care has been taken that error messages are useful and the code is
* well testable (when compiled with -DTEST_PARSER it will output to stdout
* instead of actually calling any function).
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdbool.h>
#include <stdint.h>
#include "all.h"
// Macros to make the YAJL API a bit easier to use.
#define y(x, ...) yajl_gen_ ## x (command_output.json_gen, ##__VA_ARGS__)
#define ystr(str) yajl_gen_string(command_output.json_gen, (unsigned char*)str, strlen(str))
/*******************************************************************************
* The data structures used for parsing. Essentially the current state and a
* list of tokens for that state.
*
* The GENERATED_* files are generated by generate-commands-parser.pl with the
* input parser-specs/commands.spec.
******************************************************************************/
#include "GENERATED_enums.h"
typedef struct token {
char *name;
char *identifier;
/* This might be __CALL */
cmdp_state next_state;
union {
uint16_t call_identifier;
} extra;
} cmdp_token;
typedef struct tokenptr {
cmdp_token *array;
int n;
} cmdp_token_ptr;
#include "GENERATED_tokens.h"
/*******************************************************************************
* The (small) stack where identified literals are stored during the parsing
* of a single command (like $workspace).
******************************************************************************/
struct stack_entry {
/* Just a pointer, not dynamically allocated. */
const char *identifier;
char *str;
};
/* 10 entries should be enough for everybody. */
static struct stack_entry stack[10];
/*
* Pushes a string (identified by 'identifier') on the stack. We simply use a
* single array, since the number of entries we have to store is very small.
*
*/
static void push_string(const char *identifier, char *str) {
for (int c = 0; c < 10; c++) {
if (stack[c].identifier != NULL)
continue;
/* Found a free slot, lets store it here. */
stack[c].identifier = identifier;
stack[c].str = str;
return;
}
/* When we arrive here, the stack is full. This should not happen and
* means theres either a bug in this parser or the specification
* contains a command with more than 10 identified tokens. */
fprintf(stderr, "BUG: commands_parser stack full. This means either a bug "
"in the code, or a new command which contains more than "
"10 identified tokens.\n");
exit(1);
}
// XXX: ideally, this would be const char. need to check if that works with all
// called functions.
static char *get_string(const char *identifier) {
DLOG("Getting string %s from stack...\n", identifier);
for (int c = 0; c < 10; c++) {
if (stack[c].identifier == NULL)
break;
if (strcmp(identifier, stack[c].identifier) == 0)
return stack[c].str;
}
return NULL;
}
static void clear_stack(void) {
DLOG("clearing stack.\n");
for (int c = 0; c < 10; c++) {
if (stack[c].str != NULL)
free(stack[c].str);
stack[c].identifier = NULL;
stack[c].str = NULL;
}
}
// TODO: remove this if it turns out we dont need it for testing.
#if 0
/*******************************************************************************
* A dynamically growing linked list which holds the criteria for the current
* command.
******************************************************************************/
typedef struct criterion {
char *type;
char *value;
TAILQ_ENTRY(criterion) criteria;
} criterion;
static TAILQ_HEAD(criteria_head, criterion) criteria =
TAILQ_HEAD_INITIALIZER(criteria);
/*
* Stores the given type/value in the list of criteria.
* Accepts a pointer as first argument, since it is 'call'ed by the parser.
*
*/
static void push_criterion(void *unused_criteria, const char *type,
const char *value) {
struct criterion *criterion = malloc(sizeof(struct criterion));
criterion->type = strdup(type);
criterion->value = strdup(value);
TAILQ_INSERT_TAIL(&criteria, criterion, criteria);
}
/*
* Clears the criteria linked list.
* Accepts a pointer as first argument, since it is 'call'ed by the parser.
*
*/
static void clear_criteria(void *unused_criteria) {
struct criterion *criterion;
while (!TAILQ_EMPTY(&criteria)) {
criterion = TAILQ_FIRST(&criteria);
free(criterion->type);
free(criterion->value);
TAILQ_REMOVE(&criteria, criterion, criteria);
free(criterion);
}
}
#endif
/*******************************************************************************
* The parser itself.
******************************************************************************/
static cmdp_state state;
#ifndef TEST_PARSER
static Match current_match;
#endif
static struct CommandResult subcommand_output;
static struct CommandResult command_output;
#include "GENERATED_call.h"
static void next_state(const cmdp_token *token) {
if (token->next_state == __CALL) {
DLOG("should call stuff, yay. call_id = %d\n",
token->extra.call_identifier);
subcommand_output.json_gen = command_output.json_gen;
subcommand_output.needs_tree_render = false;
GENERATED_call(token->extra.call_identifier, &subcommand_output);
/* If any subcommand requires a tree_render(), we need to make the
* whole parser result request a tree_render(). */
if (subcommand_output.needs_tree_render)
command_output.needs_tree_render = true;
clear_stack();
return;
}
state = token->next_state;
if (state == INITIAL) {
clear_stack();
}
}
/* TODO: Return parsing errors via JSON. */
struct CommandResult *parse_command(const char *input) {
DLOG("new parser handling: %s\n", input);
state = INITIAL;
/* A YAJL JSON generator used for formatting replies. */
#if YAJL_MAJOR >= 2
command_output.json_gen = yajl_gen_alloc(NULL);
#else
command_output.json_gen = yajl_gen_alloc(NULL, NULL);
#endif
y(array_open);
command_output.needs_tree_render = false;
const char *walk = input;
const size_t len = strlen(input);
int c;
const cmdp_token *token;
bool token_handled;
// TODO: make this testable
#ifndef TEST_PARSER
cmd_criteria_init(&current_match, &subcommand_output);
#endif
/* The "<=" operator is intentional: We also handle the terminating 0-byte
* explicitly by looking for an 'end' token. */
while ((walk - input) <= len) {
/* skip whitespace and newlines before every token */
while ((*walk == ' ' || *walk == '\t' ||
*walk == '\r' || *walk == '\n') && *walk != '\0')
walk++;
DLOG("remaining input = %s\n", walk);
cmdp_token_ptr *ptr = &(tokens[state]);
token_handled = false;
for (c = 0; c < ptr->n; c++) {
token = &(ptr->array[c]);
DLOG("trying token %d = %s\n", c, token->name);
/* A literal. */
if (token->name[0] == '\'') {
DLOG("literal\n");
if (strncasecmp(walk, token->name + 1, strlen(token->name) - 1) == 0) {
DLOG("found literal, moving to next state\n");
if (token->identifier != NULL)
push_string(token->identifier, sstrdup(token->name + 1));
walk += strlen(token->name) - 1;
next_state(token);
token_handled = true;
break;
}
continue;
}
if (strcmp(token->name, "string") == 0 ||
strcmp(token->name, "word") == 0) {
DLOG("parsing this as a string\n");
const char *beginning = walk;
/* Handle quoted strings (or words). */
if (*walk == '"') {
beginning++;
walk++;
while (*walk != '\0' && (*walk != '"' || *(walk-1) == '\\'))
walk++;
} else {
if (token->name[0] == 's') {
/* For a string (starting with 's'), the delimiters are
* comma (,) and semicolon (;) which introduce a new
* operation or command, respectively. Also, newlines
* end a command. */
while (*walk != ';' && *walk != ',' &&
*walk != '\0' && *walk != '\r' &&
*walk != '\n')
walk++;
} else {
/* For a word, the delimiters are white space (' ' or
* '\t'), closing square bracket (]), comma (,) and
* semicolon (;). */
while (*walk != ' ' && *walk != '\t' &&
*walk != ']' && *walk != ',' &&
*walk != ';' && *walk != '\r' &&
*walk != '\n' && *walk != '\0')
walk++;
}
}
if (walk != beginning) {
char *str = scalloc(walk-beginning + 1);
/* We copy manually to handle escaping of characters. */
int inpos, outpos;
for (inpos = 0, outpos = 0;
inpos < (walk-beginning);
inpos++, outpos++) {
/* We only handle escaped double quotes to not break
* backwards compatibility with people using \w in
* regular expressions etc. */
if (beginning[inpos] == '\\' && beginning[inpos+1] == '"')
inpos++;
str[outpos] = beginning[inpos];
}
if (token->identifier)
push_string(token->identifier, str);
DLOG("str is \"%s\"\n", str);
/* If we are at the end of a quoted string, skip the ending
* double quote. */
if (*walk == '"')
walk++;
next_state(token);
token_handled = true;
break;
}
}
if (strcmp(token->name, "end") == 0) {
DLOG("checking for the end token.\n");
if (*walk == '\0' || *walk == ',' || *walk == ';') {
DLOG("yes, indeed. end\n");
next_state(token);
token_handled = true;
/* To make sure we start with an appropriate matching
* datastructure for commands which do *not* specify any
* criteria, we re-initialize the criteria system after
* every command. */
// TODO: make this testable
#ifndef TEST_PARSER
if (*walk == '\0' || *walk == ';')
cmd_criteria_init(&current_match, &subcommand_output);
#endif
walk++;
break;
}
}
}
if (!token_handled) {
/* Figure out how much memory we will need to fill in the names of
* all tokens afterwards. */
int tokenlen = 0;
for (c = 0; c < ptr->n; c++)
tokenlen += strlen(ptr->array[c].name) + strlen("'', ");
/* Build up a decent error message. We include the problem, the
* full input, and underline the position where the parser
* currently is. */
char *errormessage;
char *possible_tokens = smalloc(tokenlen + 1);
char *tokenwalk = possible_tokens;
for (c = 0; c < ptr->n; c++) {
token = &(ptr->array[c]);
if (token->name[0] == '\'') {
/* A literal is copied to the error message enclosed with
* single quotes. */
*tokenwalk++ = '\'';
strcpy(tokenwalk, token->name + 1);
tokenwalk += strlen(token->name + 1);
*tokenwalk++ = '\'';
} else {
/* Any other token is copied to the error message enclosed
* with angle brackets. */
*tokenwalk++ = '<';
strcpy(tokenwalk, token->name);
tokenwalk += strlen(token->name);
*tokenwalk++ = '>';
}
if (c < (ptr->n - 1)) {
*tokenwalk++ = ',';
*tokenwalk++ = ' ';
}
}
*tokenwalk = '\0';
sasprintf(&errormessage, "Expected one of these tokens: %s",
possible_tokens);
free(possible_tokens);
/* Contains the same amount of characters as 'input' has, but with
* the unparseable part highlighted using ^ characters. */
char *position = smalloc(len + 1);
for (const char *copywalk = input; *copywalk != '\0'; copywalk++)
position[(copywalk - input)] = (copywalk >= walk ? '^' : ' ');
position[len] = '\0';
printf("%s\n", errormessage);
printf("Your command: %s\n", input);
printf(" %s\n", position);
/* Format this error message as a JSON reply. */
y(map_open);
ystr("success");
y(bool, false);
ystr("error");
ystr(errormessage);
ystr("input");
ystr(input);
ystr("errorposition");
ystr(position);
y(map_close);
free(position);
free(errormessage);
clear_stack();
break;
}
}
y(array_close);
DLOG("command_output.needs_tree_render = %d\n", command_output.needs_tree_render);
return &command_output;
}
/*******************************************************************************
* Code for building the stand-alone binary test.commands_parser which is used
* by t/187-commands-parser.t.
******************************************************************************/
#ifdef TEST_PARSER
/*
* Logs the given message to stdout while prefixing the current time to it,
* but only if the corresponding debug loglevel was activated.
* This is to be called by DLOG() which includes filename/linenumber
*
*/
void debuglog(uint64_t lev, char *fmt, ...) {
va_list args;
va_start(args, fmt);
fprintf(stderr, "# ");
vfprintf(stderr, fmt, args);
va_end(args);
}
int main(int argc, char *argv[]) {
if (argc < 2) {
fprintf(stderr, "Syntax: %s <command>\n", argv[0]);
return 1;
}
parse_command(argv[1]);
}
#endif