inflate / deflate

4 files changed, 171 insertions, 1 deletions

diff --git a/user/deflate.c b/user/deflate.c
new file mode 100644
index 0000000..35018d0
--- /dev/null
+++ b/user/deflate.c
@@ -0,0 +1,68 @@
+#include <stdio.h>
+#include <stdbool.h>
+
+int main(int argc, char **argv)
+{
+	FILE *in, *out;
+	int length_bytes = 0, length = 0, tracking = EOF, next;
+
+	if (argc != 3) {
+		fprintf(stderr, "usage: deflate in out\n");
+		return 1;
+	}
+
+	in = fopen(argv[1], "rb");
+	if (in == NULL) {
+		fprintf(stderr, "cannot read: %s\n", argv[1]);
+		return 1;
+	}
+
+	out = fopen(argv[2], "wb");
+	if (out == NULL) {
+		fprintf(stderr, "cannot write %s\n", argv[2]);
+		return 1;
+	}
+
+	while (next = getc(in), next != EOF) {
+		int diff;
+
+		if (tracking == EOF) {
+			tracking = next;
+			length = 1;
+			length_bytes = 0;
+			continue;
+		}
+
+		diff = tracking - next;
+		diff = diff < 1 ? -diff : diff;
+		if (diff < 2)
+			next = tracking;
+
+		if (tracking == next) {
+			length++;
+			if (length == 255) {
+				length_bytes++;
+				length = 0;
+			}
+			continue;
+		}
+
+		// write output
+		for (int i = 0; i < length_bytes; i++)
+			putc(255, out);
+		putc(length, out);
+		putc(tracking, out);
+		tracking = next;
+		length = 1;
+		length_bytes = 0;
+	}
+
+	if (length) {
+		for (int i = 0; i < length_bytes; i++)
+			putc(255, out);
+		putc(length, out);
+		putc(tracking, out);
+	}
+
+	return 0;
+}
diff --git a/user/include/unistd.h b/user/include/unistd.h
index f080917..cad3a81 100644
--- a/user/include/unistd.h
+++ b/user/include/unistd.h
@@ -16,6 +16,20 @@
 
 typedef unsigned short pid_t;
 
+enum {
+	S_SET = 0,
+	S_CUR = 1,
+	S_END = 2,
+};
+
+enum {
+	O_CREATE = 0x01,
+	O_RDONLY = 0x02,
+	O_WRONLY = 0x04,
+	O_APPEND = 0x08,
+	O_RDWR = O_RDONLY | O_WRONLY,
+};
+
 /**
  * terminates the calling process and does not return.
  *
@@ -65,7 +79,7 @@ extern void exec(const char *filename, char **args);
  * @param filename - the name of the file to open
  * @return the file descriptior of the open file or a negative error code.
  */
-extern int open(const char *filename);
+extern int open(const char *filename, int flags);
 
 /**
  * closes a stream with the given file descriptior
@@ -95,6 +109,16 @@ extern int read(int fd, void *buffer, size_t nbytes);
 extern int write(int fd, const void *buffer, size_t nbytes);
 
 /**
+ * seek a file
+ *
+ * @param fd - file stream to seek
+ * @param off - offset to seek
+ * @param whence - whence to seek
+ * @return 0 on success, or an error code
+ */
+extern int seek(int fd, long int off, int whence);
+
+/**
  * gets the pid of the calling process
  *
  * @return the pid of this process
diff --git a/user/inflate.c b/user/inflate.c
new file mode 100644
index 0000000..2f7a3d6
--- /dev/null
+++ b/user/inflate.c
@@ -0,0 +1,41 @@
+#include <stdio.h>
+#include <stdbool.h>
+
+int main(int argc, char **argv)
+{
+	FILE *in, *out;
+	int length, value;
+
+	if (argc != 3) {
+		fprintf(stderr, "usage: inflate in out\n");
+		return 1;
+	}
+
+	in = fopen(argv[1], "rb");
+	if (in == NULL) {
+		fprintf(stderr, "cannot read: %s\n", argv[1]);
+		return 1;
+	}
+
+	out = fopen(argv[2], "wb");
+	if (out == NULL) {
+		fprintf(stderr, "cannot write %s\n", argv[2]);
+		return 1;
+	}
+
+	while (1) {
+		length = getc(in);
+		value = getc(in);
+
+		if (length == EOF)
+			break;
+
+		if (value == EOF)
+			return 1;
+
+		for (int i = 0; i < length; i++)
+			putc(value, out);
+	}
+
+	return 0;
+}
diff --git a/user/lib/fopen.c b/user/lib/fopen.c
new file mode 100644
index 0000000..cb2529f
--- /dev/null
+++ b/user/lib/fopen.c
@@ -0,0 +1,37 @@
+#include <stdio.h>
+#include <unistd.h>
+
+FILE *fopen(const char *restrict filename, const char *restrict modes)
+{
+	int flags = 0;
+	int fd;
+
+	char c;
+	while (c = *modes, c) {
+		switch (c) {
+		case 'r':
+			flags |= O_RDONLY;
+			break;
+		case 'w':
+			flags |= O_CREATE | O_WRONLY;
+			break;
+		case 'a':
+			flags |= O_APPEND;
+			break;
+		case '+':
+			flags |= O_RDWR;
+			break;
+		default:
+			return NULL;
+		}
+	}
+
+	if (flags == 0)
+		return NULL;
+
+	fd = open(filename, flags);
+	if (fd < 0)
+		return NULL;
+
+	return (FILE *)(uintptr_t)fd;
+}