1 files changed, 42 insertions, 0 deletions
diff --git a/compiler/rustc_data_structures/src/base_n.rs b/compiler/rustc_data_structures/src/base_n.rs
new file mode 100644
index 000000000..3c7bea271
--- /dev/null
+++ b/compiler/rustc_data_structures/src/base_n.rs
@@ -0,0 +1,42 @@
+/// Converts unsigned integers into a string representation with some base.
+/// Bases up to and including 36 can be used for case-insensitive things.
+use std::str;
+
+#[cfg(test)]
+mod tests;
+
+pub const MAX_BASE: usize = 64;
+pub const ALPHANUMERIC_ONLY: usize = 62;
+pub const CASE_INSENSITIVE: usize = 36;
+
+const BASE_64: &[u8; MAX_BASE as usize] =
+    b"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ@$";
+
+#[inline]
+pub fn push_str(mut n: u128, base: usize, output: &mut String) {
+    debug_assert!(base >= 2 && base <= MAX_BASE);
+    let mut s = [0u8; 128];
+    let mut index = 0;
+
+    let base = base as u128;
+
+    loop {
+        s[index] = BASE_64[(n % base) as usize];
+        index += 1;
+        n /= base;
+
+        if n == 0 {
+            break;
+        }
+    }
+    s[0..index].reverse();
+
+    output.push_str(str::from_utf8(&s[0..index]).unwrap());
+}
+
+#[inline]
+pub fn encode(n: u128, base: usize) -> String {
+    let mut s = String::new();
+    push_str(n, base, &mut s);
+    s
+}