1 files changed, 108 insertions, 0 deletions
diff --git a/src/packet/header.c b/src/packet/header.c
new file mode 100644
index 0000000..b74ebb1
--- /dev/null
+++ b/src/packet/header.c
@@ -0,0 +1,108 @@
+#include "header.h"
+#include "buffer.h"
+
+#include <netinet/in.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <arpa/inet.h>
+
+uint8_t rescode_to_id(ResultCode code) {
+    switch(code) {
+        case NOERROR:
+            return 0;
+        case FORMERR:
+            return 1;
+        case SERVFAIL:
+            return 2;
+        case NXDOMAIN:
+            return 3;
+        case NOTIMP:
+            return 4;
+        case REFUSED:
+            return 5;
+        default:
+            return 2;
+    }
+}
+
+ResultCode rescode_from_id(uint8_t id) {
+    switch(id) {
+        case 0:
+            return NOERROR;
+        case 1:
+            return FORMERR;
+        case 2:
+            return SERVFAIL;
+        case 3:
+            return NXDOMAIN;
+        case 4:
+            return NOTIMP;
+        case 5:
+            return REFUSED;
+        default:
+            return FORMERR;
+    }
+}
+
+const char* str_from_code(ResultCode code) {
+    switch(code) {
+        case NOERROR: return "NOERROR";
+        case FORMERR: return "FORMERR";
+        case SERVFAIL: return "SERVFAIL";
+        case NXDOMAIN: return "NXDOMAIN";
+        case NOTIMP: return "NOTIMP";
+        case REFUSED: return "REFUSED";
+        default: return "????";
+    }
+}
+
+#define MAX(var, max) var = var > max ? max : var;
+
+void read_header(PacketBuffer* buffer, Header* header) {
+    // memset(header, 0, sizeof(Header));
+    header->id = buffer_read_short(buffer);
+
+    uint8_t a = buffer_read(buffer);
+    header->recursion_desired = (a & (1 << 0)) > 0;
+    header->truncated_message = (a & (1 << 1)) > 0;
+    header->authorative_answer = (a & (1 << 2)) > 0;
+    header->opcode = (a >> 3) & 0x0F;
+    header->response = (a & (1 << 7)) > 0;
+
+    uint8_t b = buffer_read(buffer);
+    header->rescode = rescode_from_id(b & 0x0F);
+    header->checking_disabled = (b & (1 << 4)) > 0;
+    header->authed_data = (b& (1 << 4)) > 0;
+    header->z = (b & (1 << 6)) > 0;
+    header->recursion_available = (b & (1 << 7)) > 0;
+    header->questions = buffer_read_short(buffer);
+    header->answers = buffer_read_short(buffer);
+    header->authoritative_entries = buffer_read_short(buffer);
+    header->resource_entries = buffer_read_short(buffer);
+}
+
+void write_header(PacketBuffer* buffer, Header* header) {
+    buffer_write_short(buffer, header->id);
+
+    buffer_write(buffer,
+        ((uint8_t) header->recursion_desired) |
+        ((uint8_t) header->truncated_message << 1) |
+        ((uint8_t) header->authorative_answer << 2) |
+        (header->opcode << 3) |
+        ((uint8_t) header->response << 7) 
+    );
+
+    buffer_write(buffer, 
+        (rescode_to_id(header->rescode)) |
+        ((uint8_t) header->checking_disabled << 4) |
+        ((uint8_t) header->authed_data << 5) |
+        ((uint8_t) header->z << 6) |
+        ((uint8_t) header->recursion_available << 7) 
+    );
+
+    buffer_write_short(buffer, header->questions);
+    buffer_write_short(buffer, header->answers);
+    buffer_write_short(buffer, header->authoritative_entries);
+    buffer_write_short(buffer, header->resource_entries);
+}