Added benchmark skeleton, and at least stubs for all of the necessary functions

src/benchmark.c

@@ -0,0 +1,88 @@
+#include <stdio.h>
+#include <time.h>
+#include <string.h>
+#include "hammer.h"
+
+/*
+  Usage:
+  Create your parser (i.e., HParser*), and then call
+
+  HBenchmarkResults* results = h_benchmark(parser, testcases);
+
+  Then, you can format a report with:
+
+  h_benchmark_report(stdout, results);
+
+  or just generate code to make the parser run as fast as possible with:
+
+  h_benchmark_dump_optimized_code(stdout, results);
+
+*/
+
+
+HBenchmarkResults *h_benchmark(HParser* parser, HParserTestcase* testcases) {
+  // For now, just output the results to stderr
+  HParserTestcase* tc = testcases;
+  HParserBackend backend = PB_MIN;
+
+  for (backend = PB_MIN; backend < PB_MAX; backend++) {
+    fprintf(stderr, "Compiling for backend %d ... ", backend);
+    // Step 1: Compile grammar for given parser...
+    if (h_compile(parser, PB_MIN, NULL) == -1) {
+      // backend inappropriate for grammar...
+      fprintf(stderr, "failed\n");
+      continue;
+    }
+    int tc_failed = 0;
+    // Step 1: verify all test cases.
+    for (tc = testcases; tc->input != NULL; tc++) {
+      HParseResult *res = h_parse(parser, tc->input, tc->length);
+      char* res_unamb;
+      if (res != NULL) {
+	res_unamb = h_write_result_unamb(res->ast);
+      } else
+	res_unamb = NULL;
+      if ((res_unamb == NULL && tc->output_unambiguous == NULL)
+	  || (strcmp(res_unamb, tc->output_unambiguous) != 0)) {
+	// test case failed...
+	fprintf(stderr, "failed\n");
+	// We want to run all testcases, for purposes of generating a
+	// report. (eg, if users are trying to fix a grammar for a
+	// faster backend)
+	tc_failed++;
+      }
+      h_parse_result_free(res);
+    }
+
+    if (tc_failed > 0) {
+      // Can't use this parser; skip to the next
+      fprintf(stderr, "Backend failed testcases; skipping benchmark\n");
+      continue;
+    }
+
+    for (tc = testcases; tc->input != NULL; tc++) {
+      // The goal is to run each testcase for at least 50ms each
+      // TODO: replace this with a posix timer-based benchmark. (cf. timerfd_create, timer_create, setitimer)
+      int count = 1, cur;
+      struct timespec ts_start, ts_end;
+      long long time_diff;
+      do {
+	count *= 2; // Yes, this means that the first run will run the function twice. This is fine, as we want multiple runs anyway.
+	clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts_start);
+	for (cur = 0; cur < count; cur++) {
+	  h_parse_result_free(h_parse(parser, tc->input, tc->length));
+	}
+	clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts_end);
+	
+	// time_diff is in ns
+	time_diff = (ts_end.tv_sec - ts_start.tv_sec) * 1000000000 + (ts_end.tv_nsec - ts_start.tv_nsec);
+      } while (time_diff < 100000000);
+      fprintf(stderr, "Case %d: %lld ns/parse\n", (int)(tc - testcases),  time_diff / count);
+    }
+  }
+  return NULL;
+}
+
+void h_benchmark_report(FILE* stream, HBenchmarkResults* result) {
+  // TODO: fill in this function
+}