Add a Row struct

postgres-shared/src/lib.rs

@@ -6,8 +6,11 @@ extern crate phf;
 extern crate postgres_protocol;
 
 use fallible_iterator::{FallibleIterator, FromFallibleIterator};
+use std::ascii::AsciiExt;
 use std::ops::Range;
 
+use types::Type;
+
 pub mod error;
 pub mod params;
 pub mod types;
@@ -54,3 +57,67 @@ impl RowData {
         }
     }
 }
+
+pub struct Column {
+    name: String,
+    type_: Type,
+}
+
+impl Column {
+    #[doc(hidden)]
+    pub fn new(name: String, type_: Type) -> Column {
+        Column {
+            name: name,
+            type_: type_,
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn type_(&self) -> &Type {
+        &self.type_
+    }
+}
+
+/// A trait implemented by types that can index into columns of a row.
+pub trait RowIndex {
+    /// Returns the index of the appropriate column, or `None` if no such
+    /// column exists.
+    fn idx(&self, stmt: &[Column]) -> Option<usize>;
+}
+
+impl RowIndex for usize {
+    #[inline]
+    fn idx(&self, stmt: &[Column]) -> Option<usize> {
+        if *self >= stmt.len() {
+            None
+        } else {
+            Some(*self)
+        }
+    }
+}
+
+impl<'a> RowIndex for str {
+    #[inline]
+    fn idx(&self, stmt: &[Column]) -> Option<usize> {
+        if let Some(idx) = stmt.iter().position(|d| d.name() == self) {
+            return Some(idx);
+        };
+
+        // FIXME ASCII-only case insensitivity isn't really the right thing to
+        // do. Postgres itself uses a dubious wrapper around tolower and JDBC
+        // uses the US locale.
+        stmt.iter().position(|d| d.name().eq_ignore_ascii_case(self))
+    }
+}
+
+impl<'a, T> RowIndex for &'a T
+    where T: RowIndex
+{
+    #[inline]
+    fn idx(&self, columns: &[Column]) -> Option<usize> {
+        T::idx(*self, columns)
+    }
+}