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Diffstat (limited to 'src/mds-kbdc/variables.c')
| -rw-r--r-- | src/mds-kbdc/variables.c | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/src/mds-kbdc/variables.c b/src/mds-kbdc/variables.c new file mode 100644 index 0000000..b53569a --- /dev/null +++ b/src/mds-kbdc/variables.c @@ -0,0 +1,197 @@ +/** + * mds — A micro-display server + * Copyright © 2014 Mattias Andrée (maandree@member.fsf.org) + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ +#include "variables.h" + +#include <stdlib.h> +#include <string.h> + + + +/** + * The state of a variable + */ +typedef struct variable +{ + /** + * The current value of the variable + */ + mds_kbdc_tree_t* value; + + /** + * The previous version of variable, + * before it was shadowed + */ + struct variable* restrict previous; + + /** + * The original scope the current shadow + * of the variable was created in + */ + size_t scope; + +} variable_t; + + + +/** + * Map (by index) of defined variables + */ +static variable_t** restrict variables = NULL; + +/** + * The size of `variables` + */ +static size_t variable_count = 0; + +/** + * The current scope, the number of + * times the variable-stakc has been + * pushed without being popped + */ +static size_t current_scope = 0; + + + +/** + * Destroy the variable storage + */ +void variables_terminate(void) +{ + size_t i; + variable_t* old; + for (i = 0; i < variable_count; i++) + while (variables[i]) + { + old = variables[i]; + variables[i] = variables[i]->previous; + mds_kbdc_tree_free(old->value); + free(old); + } + free(variables), variables = NULL; + variable_count = current_scope = 0; +} + + +/** + * Push the variable-stack, making it + * possible to shadow all variables + */ +void variables_stack_push(void) +{ + current_scope++; +} + + +/** + * Undo the actions of `variables_stack_push` + * and all additions to the variable storage + * since it was last called (without a + * corresponding call to this function) + */ +void variables_stack_pop(void) +{ + size_t i; + variable_t* old; + for (i = 0; i < variable_count; i++) + if (variables[i] && (variables[i]->scope == current_scope)) + { + old = variables[i]; + variables[i] = variables[i]->previous; + mds_kbdc_tree_free(old->value); + free(old); + } + current_scope--; +} + + +/** + * Check whether a let will override a variable + * rather the define or shadow it + * + * @param variable The variable index + * @return Whether a let will override the variable + */ +int variables_let_will_override(size_t variable) +{ + if (variable >= variable_count) return 0; + if (variables[variable] == NULL) return 0; + return variables[variable]->scope == current_scope; +} + + +/** + * Assign a value to a variable, and define or shadow it in the process + * + * @param variable The variable index + * @param value The variable's new value + * @return Zero on success, -1 on error + */ +int variables_let(size_t variable, mds_kbdc_tree_t* restrict value) +{ + variable_t** new; + variable_t* previous; + + /* Grow the table if necessary to fit the variable. */ + if (variable >= variable_count) + { + new = realloc(variables, (variable + 1) * sizeof(variable_t*)); + if (new == NULL) + return -1; + variables = new; + memset(variables, 0, (variable + 1 - variable_count) * sizeof(variable_t*)); + variable_count = variable + 1; + } + + if (variables_let_will_override(variable)) + { + /* Override. */ + mds_kbdc_tree_free(variables[variable]->value); + variables[variable]->value = value; + } + else + { + /* Shadow or define. */ + previous = variables[variable]; + variables[variable] = malloc(sizeof(variable_t)); + if (variables[variable] == NULL) + return variables[variable] = previous, -1; + variables[variable]->value = value; + variables[variable]->previous = previous; + variables[variable]->scope = current_scope; + } + + return 0; +} + + +/** + * Get the value currently assigned to a variable + * + * The function cannot fail, `NULL` is however returned + * if the variable is not defined + * + * @param variable The variable index + * @return The variable's value, `NULL` if not defined + */ +mds_kbdc_tree_t* variables_get(size_t variable) +{ + if (variable >= variable_count) return NULL; + if (variables[variable] == NULL) return NULL; + return variables[variable]->value; +} + |