1 files changed, 43 insertions, 0 deletions
diff --git a/vendor/windows-metadata/src/imp.rs b/vendor/windows-metadata/src/imp.rs
new file mode 100644
index 000000000..27a735a45
--- /dev/null
+++ b/vendor/windows-metadata/src/imp.rs
@@ -0,0 +1,43 @@
+#[repr(C)]
+#[derive(Default)]
+pub struct METADATA_HEADER {
+    pub signature: u32,
+    pub major_version: u16,
+    pub minor_version: u16,
+    pub reserved: u32,
+    pub length: u32,
+    pub version: [u8; 20],
+    pub flags: u16,
+    pub streams: u16,
+}
+
+pub const METADATA_SIGNATURE: u32 = 0x424A_5342;
+
+/// A coded index (see codes.rs) is a table index that may refer to different tables. The size of the column in memory
+/// must therefore be large enough to hold an index for a row in the largest possible table. This function determines
+/// this size for the given winmd file.
+pub fn coded_index_size(tables: &[usize]) -> usize {
+    fn small(row_count: usize, bits: u8) -> bool {
+        (row_count as u64) < (1u64 << (16 - bits))
+    }
+
+    fn bits_needed(value: usize) -> u8 {
+        let mut value = value - 1;
+        let mut bits: u8 = 1;
+        while {
+            value >>= 1;
+            value != 0
+        } {
+            bits += 1;
+        }
+        bits
+    }
+
+    let bits_needed = bits_needed(tables.len());
+
+    if tables.iter().all(|table| small(*table, bits_needed)) {
+        2
+    } else {
+        4
+    }
+}