1 files changed, 134 insertions, 0 deletions
diff --git a/main_2.c b/main_2.c
new file mode 100644
index 0000000..8f6fb71
--- /dev/null
+++ b/main_2.c
@@ -0,0 +1,134 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+
+#ifdef PIPE_GNUPLOT
+	#include <unistd.h>
+	#include <fcntl.h>
+#endif // PIPE_GNUPLOT
+
+#ifdef DYNAMIC_LOAD
+	#include <dlfcn.h>
+void* handle = NULL;
+#endif // DYNAMIC_LOAD
+
+struct dval {
+	double x, y;
+};
+
+typedef double (*func_t)(double);
+
+double sin2(double x) {
+	double y = sin(x);
+	return y*y;
+}
+
+double cos2(double x) {
+	double y = cos(x);
+	return y*y;
+}
+
+double __sincos(double x) {
+	// sin(x)cos(x) = sin(2x)/2
+	return sin(2*x)/2;
+}
+
+struct dval* get_table(func_t f, double start, double end, double step, long *length) {
+	long tlength = lround((end-start)/step);
+	struct dval* vals = calloc(tlength, sizeof(struct dval));
+	for (long i = 0; i < tlength; ++i) {
+		double x = start + step * i;
+		// Not accumulative because if step is too small, 
+		// start will never increment
+		vals[i] = (struct dval){.x = x, .y = f(x)};
+	}
+	*length = tlength;
+	return vals;
+}
+
+void print_help(int status) {
+	const char *help = 
+		"Usage: ./task2 -f func_name -o output_file [-h]\n"
+		"\t-h: this help\n"
+		"\t-f: function: either 'sin2', 'cos2' or 'sincos'.\n"
+		"\t\tif compiled with -DDYNAMIC_LOAD, file name with dynamic function.\n"
+		"\t-o: output file.\n\n"
+		"NOTE: the function in dynamic library must be named 'f'.\n"
+		"NOTE 2: with flag -DPIPE_GNUPLOT output will be piped in gnuplot\n.";
+	puts(help);
+	exit(status);
+}
+
+func_t get_function(const char* name) {
+	if (!strcmp(name, "cos2"))
+		return &cos2;
+	if (!strcmp(name, "sin2"))
+		return &sin2;
+	if (!strcmp(name, "sincos"))
+		return &__sincos;
+#ifndef DYNAMIC_LOAD
+	fputs("ERROR: unknown function. To use dynamic loading, compile with `-DDYNAMIC_LOAD`.\n", stderr);
+	exit(EXIT_FAILURE);
+#else  // DYNAMIC_LOAD
+	handle = dlopen(name, RTLD_NOW);
+	if (!handle) goto fail;
+	func_t f = dlsym(handle, "f");
+	if (!f) goto fail;
+	return f;
+fail:
+	fputs(dlerror(), stderr);
+	exit(EXIT_FAILURE);
+#endif // DYNAMIC_LOAD
+}
+
+void print_table(FILE* stream, const struct dval *table, long size) {
+	for (long i = 0; i < size; ++i) {
+		fprintf(stream, "%lg %lg\n", table[i].x, table[i].y);
+	}
+}
+
+int main(int argc, char *argv[]) {
+	func_t function = NULL;
+	const char *out = NULL;
+	for (int i = 1; i < argc; ++i) {
+		if (!strcmp(argv[i], "-h"))
+			print_help(EXIT_SUCCESS);
+		else if (!strcmp(argv[i], "-f"))
+			function = get_function(argv[++i]);
+		else if (!strcmp(argv[i], "-o"))
+			out = argv[++i];
+		else print_help(EXIT_FAILURE);
+	}
+	if (!function || !out) print_help(EXIT_SUCCESS);
+	long table_len;
+	struct dval *table = get_table(function, 0, 3, 0.01, &table_len);
+	print_table(stdout, table, table_len);
+	FILE *f = fopen(out, "w+");
+	if (f) { 
+		print_table(f, table, table_len);
+		fflush(f);
+	}
+	else perror(out);
+
+#ifdef PIPE_GNUPLOT 
+	FILE* gp = popen("gnuplot", "w");
+	if (!gp) goto exit;
+	fputs("plot '-' with lines\n", gp);
+	print_table(gp, table, table_len);
+	fputs("e\n", gp);
+	fflush(gp);
+
+	getchar();
+	pclose(gp);
+#endif // PIPE_GNUPLOT
+
+exit:
+	fclose(f);
+	free(table);
+#ifdef DYNAMIC_LOAD
+	if (handle) dlclose(handle);
+#endif // DYNAMIC_LOAD
+	exit(EXIT_SUCCESS);
+}
+