commit 9ee3410975ebe26cc448e6c379860b68afaad25e
Author: Alessandro Mauri <alemauri001@gmail.com>
Date:   Mon Apr 13 23:29:21 2020 +0200

    first working prototype

diff --git a/.gitignore b/.gitignore
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+*.out
diff --git a/.macrod.c.swp b/.macrod.c.swp
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diff --git a/README.md b/README.md
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diff --git a/macrod.c b/macrod.c
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+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+/* Standard errors */
+#include <errno.h>
+/* Directory control */
+#include <sys/types.h>
+#include <dirent.h>
+
+#ifdef __linux__
+	#include <linux/input.h>
+#endif 
+#ifdef __FreeBSD__
+	#include <dev/evdev/input.h>
+#endif
+
+struct pressed_buffer {
+	unsigned short *buf;
+	unsigned int size;
+};
+
+int pressBufferAdd (struct pressed_buffer*, unsigned short);
+int pressBufferRemove (struct pressed_buffer*, unsigned short);
+
+int main (void) // remember getopt() to automaically parse options
+{
+	FILE *fp;
+	fp = fopen("/dev/input/event0", "r");
+	if (fp == NULL) {
+		fputs(strerror(errno), stderr); 
+		exit(errno);
+	}
+
+	struct input_event event;
+	struct pressed_buffer pb = {NULL, 0}; // Pressed keys buffer	
+
+	while (!ferror(fp)) {
+		fread(&event, sizeof(struct input_event), 1, fp);
+		if (event.type == EV_KEY) {
+			
+			switch (event.value) {
+				case (0): // Key release
+					pressBufferRemove(&pb, event.code);
+					break;
+				case (1): // Key press
+					pressBufferAdd(&pb, event.code);
+					break;
+			}
+
+			printf("Pressed keys: ");
+			for (int i = 0; i < pb.size; i++)
+				printf("%d ", pb.buf[i]);
+			putchar('\n');
+		}
+	}
+
+	if (fclose(fp) == EOF) {
+		fputs(strerror(errno), stderr);
+		exit(errno);
+	}	
+	return 0;
+}
+
+int pressBufferAdd (struct pressed_buffer *pb, unsigned short key)
+{
+/* Adds a keycode to the pressed buffer if it is not already present 
+ * Returns non zero if the key was not added. */
+	
+	if (!pb) return 1;
+	if (pb->buf != NULL) {
+		/* Linear search if the key is already buffered */
+		for (int i = 0; i < pb->size; i++)
+			if (key == pb->buf[i]) return 1;
+	}
+	
+	unsigned short *b;
+		b = realloc(pb->buf, sizeof(unsigned short) * pb->size + 1);
+	if (!b) {
+		fprintf(stderr, "realloc failed in pressBufferAdd: %s", strerror(errno));
+		exit(errno);
+	}
+	pb->buf = b;
+	pb->buf[pb->size++] = key;
+
+	return 0;
+}
+
+int pressBufferRemove (struct pressed_buffer *pb, unsigned short key)
+{
+/* Removes a keycode from a pressed buffer if it is present returns 
+ * non zero in case of failure (key not present or buffer empty). */
+	if (!pb) return 1;
+	
+	for (int i = 0; i < pb->size; i++) {
+		if (pb->buf[i] == key) {
+			pb->size--;
+			pb->buf[i] = pb->buf[pb->size];
+			unsigned short *b;
+			b = realloc(pb->buf, sizeof(unsigned short) * pb->size);
+			if (!b && pb->size) {
+				fprintf(stderr, "realloc failed in pressBufferRemove: %s",
+							strerror(errno));
+				exit(errno);
+			}
+			pb->buf = b;
+			return 0;
+		}
+	}
+
+	return 1;
+}