added support for http headers in requests (#13)

examples/httpbin.rs

@@ -1,7 +1,12 @@
 use blockless_sdk::*;
 
 fn main() {
-    let opts = HttpOptions::new("GET", 30, 10);
+    let mut opts = HttpOptions::new("GET", 30, 10);
+    opts.headers = Some(std::collections::BTreeMap::from([(
+        "X-Test".to_string(),
+        "123".to_string(),
+    )]));
+
     let http = BlocklessHttp::open("http://httpbin.org/anything", &opts);
     let http = http.unwrap();
     let body = http.get_all_body().unwrap();
@@ -10,6 +15,7 @@ fn main() {
         json::JsonValue::Object(o) => o,
         _ => panic!("must be object"),
     };
+
     let headers = match bodies.get("headers") {
         Some(json::JsonValue::Object(headers)) => headers,
         _ => panic!("must be array"),

src/http.rs

@@ -1,7 +1,6 @@
-use std::cmp::Ordering;
-
 use crate::{error::HttpErrorKind, http_host::*};
 use json::JsonValue;
+use std::{cmp::Ordering, collections::BTreeMap};
 
 pub type Handle = u32;
 
@@ -17,6 +16,7 @@ pub struct HttpOptions {
     pub connect_timeout: u32,
     pub read_timeout: u32,
     pub body: Option<String>,
+    pub headers: Option<BTreeMap<String, String>>,
 }
 
 impl HttpOptions {
@@ -26,15 +26,27 @@ impl HttpOptions {
             connect_timeout,
             read_timeout,
             body: None,
+            headers: None,
         }
     }
 
     pub fn dump(&self) -> String {
+        // convert BTreeMap to json string
+        let mut headers_str = self
+            .headers
+            .clone()
+            .unwrap_or_default()
+            .iter()
+            .map(|(k, v)| format!("\"{}\":\"{}\"", k, v))
+            .collect::<Vec<String>>()
+            .join(",");
+        headers_str = format!("{{{}}}", headers_str);
+
         let mut json = JsonValue::new_object();
         json["method"] = self.method.clone().into();
         json["connectTimeout"] = self.connect_timeout.into();
         json["readTimeout"] = self.read_timeout.into();
-        json["headers"] = "{}".into();
+        json["headers"] = headers_str.into();
         json["body"] = self.body.clone().into();
         json.dump()
     }

src/memory_host.rs

@@ -1,4 +1,3 @@
-
 #[link(wasm_import_module = "blockless_memory")]
 extern "C" {
     #[link_name = "memory_read"]