From fa0361344ce4a23569216633385c1af4c9cf8fb7 Mon Sep 17 00:00:00 2001
From: Noah Metz <noah@metznet.ca>
Date: Fri, 5 Jan 2024 15:48:13 -0700
Subject: [PATCH] Initial commit

---
 Makefile |   2 +
 main.c   | 159 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 161 insertions(+)
 create mode 100644 Makefile
 create mode 100644 main.c

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..d698de6
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,2 @@
+main: main.c
+	gcc -o main main.c
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..e2adaa5
--- /dev/null
+++ b/main.c
@@ -0,0 +1,159 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <strings.h>
+#include <stdlib.h>
+
+const char * http_version_str = "HTTP/1.1 ";
+
+typedef struct http_header {
+  uint8_t * status_code_ptr;
+  size_t status_code_len;
+
+  size_t num_headers;
+  uint8_t ** header_key_ptrs;
+  size_t * header_key_lens;
+  uint8_t ** header_val_ptrs;
+  size_t * header_val_lens;
+
+  uint8_t * body_ptr;
+  size_t body_len;
+} http_header_t;
+
+http_header_t * parse_header(uint8_t * data, size_t len) {
+  http_header_t * ret = malloc(sizeof(http_header_t));
+
+  // Parse version
+  if(len < strlen(http_version_str)) {
+    fprintf(stderr, "Data shorter than version string\n");
+    return 0;
+  } else if(strncmp((const char *)data, http_version_str, strlen(http_version_str)) != 0) {
+    fprintf(stderr, "http_version_str did not match\n");
+    return 0;
+  }
+
+  size_t ptr = strlen(http_version_str);
+
+  // Prase status code
+  size_t status_code_start = ptr;
+  size_t status_code_end = 0;
+  while(ptr < len-1) {
+    if((data[ptr] == '\r') && (data[ptr+1] == '\n')) {
+      status_code_end = ptr;
+      ptr += 2;
+      break;
+    } else {
+      ptr += 1;
+    }
+  }
+
+  if(ptr >= (len-1)) {
+    fprintf(stderr, "Reached EOF while parsing status code\n");
+    return 0;
+  } else {
+    ret->status_code_ptr = data + status_code_start;
+    ret->status_code_len = status_code_end - status_code_start;
+  }
+
+  if(ptr < len-1) {
+    if((data[ptr] == '\r') && (data[ptr+1] == '\n')) {
+      ret->num_headers = 0;
+      return ret;
+    }
+  }
+
+  // Parse header
+  size_t num_headers = 0;
+  uint8_t * header_key_ptrs[1024];
+  uint8_t * header_val_ptrs[1024];
+  size_t header_key_lens[1024];
+  size_t header_val_lens[1024];
+  while(ptr < len-1) {
+    size_t key_start = ptr;
+    size_t key_len = 0;
+    while(ptr < len-1) {
+      if(data[ptr] == ':') {
+        key_len = ptr - key_start;
+        ptr += 1;
+        break;
+      } else {
+        ptr += 1; 
+      }
+    }
+
+    if(ptr >= len-1) {
+      fprintf(stderr, "Reached EOF reading header key\n");
+      return 0;
+    }
+
+    size_t val_start = ptr;
+    size_t val_len = 0;
+    while(ptr < len-1) {
+      if((data[ptr] == '\r') && (data[ptr+1] == '\n')) {
+        val_len = ptr - val_start;
+        ptr += 2;
+        break;
+      } else {
+        ptr += 1; 
+      }
+    }
+
+    if(ptr >= len-1) {
+      fprintf(stderr, "Reached EOF reading header val\n");
+      return 0;
+    }
+
+    header_key_ptrs[num_headers] = &data[key_start];
+    header_key_lens[num_headers] = key_len;
+    header_val_ptrs[num_headers] = &data[val_start];
+    header_val_lens[num_headers] = val_len;
+
+    num_headers += 1;
+
+    if(ptr < len-1) {
+      if((data[ptr] == '\r') && (data[ptr+1] == '\n')) {
+        ptr += 2;
+        break;
+      }
+    }
+  }
+
+  ret->num_headers = num_headers;
+
+  ret->header_key_ptrs = malloc(sizeof(uint8_t*)*num_headers);
+  ret->header_key_lens = malloc(sizeof(size_t)*num_headers);
+
+  ret->header_val_ptrs = malloc(sizeof(uint8_t*)*num_headers);
+  ret->header_val_lens = malloc(sizeof(size_t)*num_headers);
+
+  for(size_t i = 0; i < num_headers; i++) {
+    ret->header_key_ptrs[i] = header_key_ptrs[i];
+    ret->header_key_lens[i] = header_key_lens[i];
+
+    ret->header_val_ptrs[i] = header_val_ptrs[i];
+    ret->header_val_lens[i] = header_val_lens[i];
+  }
+
+  ret->body_ptr = data + ptr;
+  ret->body_len = len - ptr;
+
+  return ret;
+}
+
+int main(int argc, char ** argv) {
+  if(argc < 2) {
+    printf("Data to parse required as input\n");
+    return 1;
+  }
+
+  http_header_t * header = parse_header((uint8_t*)argv[1], strlen(argv[1]));
+  if(header == 0) {
+    fprintf(stderr, "no header returned from parse\n");
+  } else {
+    printf("Parsed header with code %.*s and %d headers\n", header->status_code_len, header->status_code_ptr, header->num_headers);
+    for(size_t i = 0; i < header->num_headers; i++) {
+      printf("Header %ld: %.*s - %.*s\n", i,header->header_key_lens[i], header->header_key_ptrs[i], header->header_val_lens[i], header->header_val_ptrs[i]);
+    }
+  }
+
+  return 0;
+}