Add a way to add headers to parts of multipart form data

src/multipart.rs

@@ -1,2 +1,2 @@
 //! # multipart/form-data
-pub use ::multipart_::{Form, Part};
+pub use ::multipart_::{Form, Part, HeaderMap};

src/multipart_.rs

@@ -7,6 +7,10 @@ use std::path::Path;
 use mime_guess::{self, Mime};
 use url::percent_encoding;
 use uuid::Uuid;
+use http;
+
+/// An alias to http::HeaderMap so http is unneded as an explicit dependency
+pub type HeaderMap = http::HeaderMap<String>;
 
 use {Body};
 
@@ -129,6 +133,7 @@ pub struct Part {
     value: Body,
     mime: Option<Mime>,
     file_name: Option<Cow<'static, str>>,
+    hdr: HeaderMap,
 }
 
 impl Part {
@@ -183,6 +188,7 @@ impl Part {
             value: value,
             mime: None,
             file_name: None,
+            hdr: HeaderMap::default()
         }
     }
 
@@ -197,6 +203,21 @@ impl Part {
         self.file_name = Some(filename.into());
         self
     }
+
+    /// Returns a reference to the map of additional header fields
+    pub fn header_fields(&self) -> &HeaderMap {
+        &self.hdr
+    }
+
+    /// Returns a mutable reference to the map of additional header fields
+    pub fn header_fields_mut(&mut self) -> &mut HeaderMap {
+        &mut self.hdr
+    }
+
+    /// Replaces the additional header fields
+    pub fn replace_header_fields(&mut self, hdr: HeaderMap) -> () {
+        self.hdr = hdr
+    }
 }
 
 impl fmt::Debug for Part {
@@ -205,6 +226,7 @@ impl fmt::Debug for Part {
             .field("value", &self.value)
             .field("mime", &self.mime)
             .field("file_name", &self.file_name)
+            .field("hdr", &self.hdr)
             .finish()
     }
 }
@@ -305,7 +327,7 @@ impl Read for Reader {
 
 fn header(name: &str, field: &Part) -> String {
     format!(
-        "Content-Disposition: form-data; {}{}{}",
+        "Content-Disposition: form-data; {}{}{}{}",
         format_parameter("name", name),
         match field.file_name {
             Some(ref file_name) => format!("; {}", format_parameter("filename", file_name)),
@@ -314,7 +336,12 @@ fn header(name: &str, field: &Part) -> String {
         match field.mime {
             Some(ref mime) => format!("\r\nContent-Type: {}", mime),
             None => "".to_string(),
-        }
+        },
+        field.hdr.iter().fold(
+            "".to_string(),
+            |hdrs, (k,v)|
+                format!("{}\r\n{}: {}", hdrs, k.as_str(), v)
+        )
     )
 }