Quiz4: HTML + JS + JSON
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2e0aaf6688
commit
7b3ddf5cc9
4
cmd.txt
4
cmd.txt
@ -8,3 +8,7 @@ doas mkdir /var/www/tmp
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doas chmod 1777 /var/www/tmp
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cc -static -g -W -Wall -o build/example4 examples/example4.c -I/usr/local/include -L/usr/local/lib -lkcgi -lkcgihtml -lz -lsqlite3
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doas install -o www -g www -m 0500 build/example4 /var/www/cgi-bin/
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cc -static -g -W -Wall -o build/quiz4 quiz4.c -I/usr/local/include -L/usr/local/lib -lkcgi -lkcgihtml -lkcgijson -lz -lsqlite3
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doas install -o www -g www -m 0500 build/quiz4 /var/www/cgi-bin/
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doas install -o www -g www -m 0500 quiz4.js /var/www/htdocs/
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368
quiz4.c
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368
quiz4.c
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@ -0,0 +1,368 @@
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/*
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* Copyright (c) 2016 Kristaps Dzonsons <kristaps@bsd.lv>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <stdint.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <kcgi.h>
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#include <kcgihtml.h>
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#include <kcgijson.h>
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#include <sqlite3.h>
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enum page {
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PAGE_INDEX, /* /index or just / */
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PAGE_JSON, /* /quiz4.json */
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PAGE__MAX
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};
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static const char *JSON_COUNT = "count";
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static const char *const pages[PAGE__MAX] = {
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"index", /* PAGE_INDEX */
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"quiz4", /* PAGE_JSON */
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};
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typedef void (*disp)(struct kreq *);
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static void sendjson(struct kreq *req);
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static void sendindex(struct kreq *req);
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static const disp disps[PAGE__MAX] = {
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sendindex, /* PAGE_INDEX */
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sendjson, /* PAGE_JSON */
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};
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/*
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* Generic routine to prime the HTTP document.
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*/
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static void
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resp_open(struct kreq *req, enum khttp http)
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{
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khttp_head(req, kresps[KRESP_STATUS],
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"%s", khttps[http]);
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khttp_head(req, kresps[KRESP_CONTENT_TYPE],
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"%s", kmimetypes[req->mime]);
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khttp_body(req);
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}
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/*
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* When the database is busy or locked, sleep for a random amount of
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* time before continuing.
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* We could put all sorts of heuristics in here to back off, but we do
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* something really simple.
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*/
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static void
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db_sleep(size_t attempt)
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{
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if (attempt < 10)
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usleep(arc4random_uniform(100000));
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else
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usleep(arc4random_uniform(500000));
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}
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/*
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* Keep trying to open the database forever.
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*/
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static sqlite3 *
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db_open(void)
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{
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size_t attempt;
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sqlite3 *db;
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int rc;
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attempt = 0;
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again:
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rc = sqlite3_open("/tmp/example4.db", &db);
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if (SQLITE_BUSY == rc) {
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db_sleep(attempt++);
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goto again;
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} else if (SQLITE_LOCKED == rc) {
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fprintf(stderr, "sqlite3_open: %s\n",
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sqlite3_errmsg(db));
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db_sleep(attempt++);
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goto again;
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} else if (SQLITE_PROTOCOL == rc) {
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fprintf(stderr, "sqlite3_open: %s\n",
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sqlite3_errmsg(db));
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db_sleep(attempt++);
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goto again;
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} else if (SQLITE_OK == rc) {
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sqlite3_busy_timeout(db, 500);
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return(db);
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}
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fprintf(stderr, "sqlite3_open: %s\n", sqlite3_errmsg(db));
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return(NULL);
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}
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/*
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* Close the database.
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*/
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static void
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db_close(sqlite3 *db)
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{
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if (SQLITE_OK == sqlite3_close(db))
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return;
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fprintf(stderr, "sqlite3_close: %s\n", sqlite3_errmsg(db));
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}
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/*
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* Step through the result set of a database query.
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*/
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static int
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db_step(sqlite3 *db, sqlite3_stmt *stmt)
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{
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int rc;
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size_t attempt = 0;
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again:
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rc = sqlite3_step(stmt);
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if (SQLITE_BUSY == rc) {
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db_sleep(attempt++);
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goto again;
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} else if (SQLITE_LOCKED == rc) {
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fprintf(stderr, "sqlite3_step: %s\n",
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sqlite3_errmsg(db));
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db_sleep(attempt++);
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goto again;
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} else if (SQLITE_PROTOCOL == rc) {
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fprintf(stderr, "sqlite3_step: %s\n",
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sqlite3_errmsg(db));
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db_sleep(attempt++);
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goto again;
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}
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if (SQLITE_DONE == rc || SQLITE_ROW == rc)
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return(rc);
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fprintf(stderr, "sqlite3_step: %s\n", sqlite3_errmsg(db));
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return(rc);
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}
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/*
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* Execute a database query.
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*/
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static int
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db_exec(sqlite3 *db, const char *sql)
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{
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size_t attempt = 0;
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int rc;
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again:
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rc = sqlite3_exec(db, sql, NULL, NULL, NULL);
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if (SQLITE_BUSY == rc) {
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db_sleep(attempt++);
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goto again;
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} else if (SQLITE_LOCKED == rc) {
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fprintf(stderr, "sqlite3_exec: %s\n",
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sqlite3_errmsg(db));
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db_sleep(attempt++);
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goto again;
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} else if (SQLITE_PROTOCOL == rc) {
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fprintf(stderr, "sqlite3_exec: %s\n",
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sqlite3_errmsg(db));
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db_sleep(attempt++);
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goto again;
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} else if (SQLITE_OK == rc)
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return(1);
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fprintf(stderr, "sqlite3_exec: %s (%s)\n",
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sqlite3_errmsg(db), sql);
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return(0);
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}
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/*
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* Prepare a database statement.
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* If we fail, try to populate the database: it might not have been
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* initialised yet.
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*/
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static sqlite3_stmt *
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db_stmt(sqlite3 *db, const char *sql, int recurse)
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{
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sqlite3_stmt *stmt;
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const char *esql;
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size_t attempt = 0;
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int rc, bailed;
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bailed = 0;
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again:
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rc = sqlite3_prepare_v2(db, sql, -1, &stmt, NULL);
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if (SQLITE_BUSY == rc) {
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db_sleep(attempt++);
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goto again;
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} else if (SQLITE_LOCKED == rc) {
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fprintf(stderr, "sqlite3_prepare_v2: %s\n",
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sqlite3_errmsg(db));
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db_sleep(attempt++);
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goto again;
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} else if (SQLITE_PROTOCOL == rc) {
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fprintf(stderr, "sqlite3_prepare_v2: %s\n",
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sqlite3_errmsg(db));
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db_sleep(attempt++);
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goto again;
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} else if (SQLITE_OK == rc)
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return(stmt);
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fprintf(stderr, "sqlite3_prepare_v2: %s (%s) (%d)\n",
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sqlite3_errmsg(db), sql, sqlite3_errcode(db));
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sqlite3_finalize(stmt);
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/*
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* Only attempt to do this if (1) we have a certain error, (2)
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* we haven't already bailed out, and (3) we haven't recursed
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* into the db_stmt() function.
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*/
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if (SQLITE_ERROR == rc && 0 == bailed && recurse) {
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esql = "CREATE TABLE record "
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"(count INTEGER NOT NULL DEFAULT(0))";
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if (db_exec(db, esql)) {
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esql = "INSERT INTO record DEFAULT VALUES";
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if (NULL != (stmt = db_stmt(db, esql, 0))) {
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db_step(db, stmt);
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sqlite3_finalize(stmt);
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}
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}
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bailed = 1;
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goto again;
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}
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return(NULL);
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}
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static void
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sendjson(struct kreq *req)
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{
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struct kjsonreq r;
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int rc;
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sqlite3 *db;
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sqlite3_stmt *stmt;
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resp_open(req, KHTTP_200);
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kjson_open(&r, req);
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kjson_obj_open(&r);
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if (NULL != (db = db_open())) {
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stmt = db_stmt(db, "SELECT count FROM record", 1);
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if (NULL != stmt) {
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rc = db_step(db, stmt);
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if (SQLITE_ROW == rc)
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kjson_putintp(&r, JSON_COUNT,
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sqlite3_column_int64(stmt, 0));
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else if (SQLITE_DONE == rc)
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kjson_putnullp(&r, JSON_COUNT);
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// TODO err khtml_puts(&r, "No value!?");
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else
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kjson_putnullp(&r, JSON_COUNT);
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// TODO err khtml_puts(&r, "Error getting value.");
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sqlite3_finalize(stmt);
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} else
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kjson_putnullp(&r, JSON_COUNT);
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// TODO err khtml_puts(&r, "Error getting statement.");
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stmt = db_stmt(db, "UPDATE record SET count=count+1", 0);
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(void)db_step(db, stmt);
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sqlite3_finalize(stmt);
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db_close(db);
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} else
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kjson_putnullp(&r, JSON_COUNT);
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// TODO err khtml_puts(&r, "Error opening database.");
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kjson_close(&r);
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}
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static void
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sendindex(struct kreq *req)
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{
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struct khtmlreq r;
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resp_open(req, KHTTP_200);
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khtml_open(&r, req);
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khtml_elem(&r, KELEM_DOCTYPE);
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khtml_elem(&r, KELEM_HTML);
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khtml_elem(&r, KELEM_HEAD);
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khtml_elem(&r, KELEM_TITLE);
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khtml_puts(&r, "Test JSON");
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khtml_closeelem(&r, 1);
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khtml_attr(&r, KELEM_SCRIPT,
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KATTR_SRC, "/quiz4.js",
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KATTR__MAX);
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khtml_closeelem(&r, 2);
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khtml_elem(&r, KELEM_BODY);
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khtml_attr(&r, KELEM_DIV,
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KATTR_ID, "count",
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KATTR__MAX);
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khtml_puts(&r, "No data.");
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khtml_close(&r);
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}
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int
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main(void)
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{
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struct kreq r;
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/*
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* Set up our main HTTP context.
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*/
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if (KCGI_OK != khttp_parse
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(&r, NULL, 0, pages, PAGE__MAX, PAGE_INDEX))
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return(EXIT_FAILURE);
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if (KMETHOD_OPTIONS == r.method) {
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/*
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* Indicate that we accept GET and POST methods.
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* This isn't really needed.
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*/
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khttp_head(&r, kresps[KRESP_STATUS],
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"%s", khttps[KHTTP_200]);
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khttp_head(&r, kresps[KRESP_ALLOW],
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"OPTIONS GET POST");
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khttp_body(&r);
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} else if (KMETHOD_GET != r.method) {
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/*
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* Don't accept non-GET and non-POST methods.
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*/
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resp_open(&r, KHTTP_405);
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} else if (PAGE__MAX == r.page ||
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( KMIME_APP_JSON != r.mime &&
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KMIME_TEXT_HTML != r.mime) ) {
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/*
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* We've been asked for an unknown page or something
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* with an unknown extension.
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*/
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resp_open(&r, KHTTP_404);
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khttp_puts(&r, "Page not found.");
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} else
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/*
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* Route to page handler.
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*/
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(*disps[r.page])(&r);
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/*
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* Clean up our context.
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*/
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khttp_free(&r);
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return(EXIT_SUCCESS);
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}
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20
quiz4.js
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20
quiz4.js
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@ -0,0 +1,20 @@
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function loadJSON(path, success, error)
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{
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var xhr = new XMLHttpRequest();
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xhr.onreadystatechange = function() {
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if (xhr.readyState === XMLHttpRequest.DONE) {
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if (xhr.status === 200) {
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success(JSON.parse(xhr.responseText));
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} else {
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error(xhr);
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}
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}
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};
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xhr.open("GET", path, true);
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xhr.send();
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}
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loadJSON('/cgi-bin/quiz4/quiz4.json',
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function(data) { document.getElementById("count").textContent = data.count; },
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function(xhr) { console.error(xhr); }
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);
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