writeout: support to generate JSON output

This commit adds support to generate JSON via the writeout feature:

    -w "%{json}"

It leverages the existing infrastructure as much as possible. Thus,
generating the JSON on STDERR is possible by:

    -w "%{stderr}%{json}"

This implements a variant of
https://github.com/curl/curl/wiki/JSON#--write-out-json.

Closes #4870

1 files changed, 181 insertions, 0 deletions

diff --git a/src/tool_writeout_json.c b/src/tool_writeout_json.c
new file mode 100644
index 000000000..99252ecb8
--- /dev/null
+++ b/src/tool_writeout_json.c
@@ -0,0 +1,181 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+#include "tool_setup.h"
+
+#define ENABLE_CURLX_PRINTF
+
+/* use our own printf() functions */
+#include "curlx.h"
+#include "tool_cfgable.h"
+#include "tool_writeout_json.h"
+#include "tool_writeout.h"
+
+
+static const char *http_version[] = {
+  "0",   /* CURL_HTTP_VERSION_NONE */
+  "1",   /* CURL_HTTP_VERSION_1_0 */
+  "1.1", /* CURL_HTTP_VERSION_1_1 */
+  "2"    /* CURL_HTTP_VERSION_2 */
+  "3"    /* CURL_HTTP_VERSION_3 */
+};
+
+static void jsonEscape(FILE *stream, const char *in)
+{
+  const char *i = in;
+  const char *in_end = in + strlen(in);
+
+  for(; i < in_end; i++) {
+    switch(*i) {
+    case '\\':
+      fputs("\\\\", stream);
+      break;
+    case '\"':
+      fputs("\\\"", stream);
+      break;
+    case '\b':
+      fputs("\\b", stream);
+      break;
+    case '\f':
+      fputs("\\f", stream);
+      break;
+    case '\n':
+      fputs("\\n", stream);
+      break;
+    case '\r':
+      fputs("\\r", stream);
+      break;
+    case '\t':
+      fputs("\\t", stream);
+      break;
+    default:
+      if (*i < 32) {
+        fprintf(stream, "u%04x", *i);
+      }
+      else {
+        fputc(*i, stream);
+      }
+      break;
+    };
+  }
+}
+
+static int writeTime(FILE *str, CURL *curl, const char *key, CURLINFO ci)
+{
+  curl_off_t val = 0;
+  if(CURLE_OK == curl_easy_getinfo(curl, ci, &val)) {
+    curl_off_t s = val / 1000000l;
+    curl_off_t ms = val % 1000000l;
+    fprintf(str, "\"%s\":%ld.%06ld", key, s, ms);
+    return 1;
+  }
+  return 0;
+}
+
+static int writeString(FILE *str, CURL *curl, const char *key, CURLINFO ci)
+{
+  char *valp = NULL;
+  if((CURLE_OK == curl_easy_getinfo(curl, ci, &valp)) && valp) {
+    fprintf(str, "\"%s\":\"", key);
+    jsonEscape(str, valp);
+    fprintf(str, "\"");
+    return 1;
+  }
+  return 0;
+}
+
+static int writeLong(FILE *str, CURL *curl, const char *key, CURLINFO ci)
+{
+  curl_off_t val = 0;
+  if(CURLE_OK == curl_easy_getinfo(curl, ci, &val)) {
+    fprintf(str, "\"%s\":%ld", key, val);
+    return 1;
+  }
+  return 0;
+}
+
+static int writeFilename(FILE *str, const char *key, const char *filename)
+{
+  if(filename) {
+    fprintf(str, "\"%s\":\"", key);
+    jsonEscape(str, filename);
+    fprintf(str, "\"");
+  }
+  else {
+    fprintf(str, "\"%s\":null", key);
+  }
+  return 1;
+}
+
+static int writeVersion(FILE *str, CURL *curl, const char *key, CURLINFO ci)
+{
+  long version = 0;
+  if(CURLE_OK == curl_easy_getinfo(curl, ci, &version) &&
+     (version >= 0) &&
+     (version < (long)(sizeof(http_version)/sizeof(char *)))) {
+    fprintf(str, "\"%s\":\"%s\"", key, http_version[version]);
+    return 1;
+  }
+  return 0;
+}
+
+void ourWriteOutJSON(const struct writeoutvar mappings[], CURL *curl,
+        struct OutStruct *outs, FILE *stream)
+{
+  int i;
+
+  fputs("{", stream);
+  for(i = 0; mappings[i].name != NULL; i++) {
+    const char *name = mappings[i].name;
+    CURLINFO cinfo = mappings[i].cinfo;
+    int ok = 0;
+
+    if(mappings[i].is_ctrl == 1) {
+      continue;
+    }
+
+    switch(mappings[i].jsontype) {
+    case JSON_STRING:
+      ok = writeString(stream, curl, name, cinfo);
+      break;
+    case JSON_LONG:
+      ok = writeLong(stream, curl, name, cinfo);
+      break;
+    case JSON_TIME:
+      ok = writeTime(stream, curl, name, cinfo);
+      break;
+    case JSON_FILENAME:
+      ok = writeFilename(stream, name, outs->filename);
+      break;
+    case JSON_VERSION:
+      ok = writeVersion(stream, curl, name, cinfo);
+      break;
+    default:
+      break;
+    }
+
+    if(ok) {
+      fputs(",", stream);
+    }
+  }
+
+  fprintf(stream, "\"curl_version\":\"%s\"}", curl_version());
+}