1 files changed, 66 insertions, 0 deletions
diff --git a/semver-parser/src/common.rs b/semver-parser/src/common.rs
new file mode 100644
index 0000000..267b4d9
--- /dev/null
+++ b/semver-parser/src/common.rs
@@ -0,0 +1,66 @@
+use version::Identifier;
+use recognize::{Recognize, Alt, OneOrMore, Inclusive, OneByte};
+use std::str::from_utf8;
+
+// by the time we get here, we know that it's all valid characters, so this doesn't need to return
+// a result or anything
+fn parse_meta(s: &str) -> Vec<Identifier> {
+    // Originally, I wanted to implement this method via calling parse, but parse is tolerant of
+    // leading zeroes, and we want anything with leading zeroes to be considered alphanumeric, not
+    // numeric. So the strategy is to check with a recognizer first, and then call parse once
+    // we've determined that it's a number without a leading zero.
+    s.split(".")
+        .map(|part| {
+            // another wrinkle: we made sure that any number starts with a
+            // non-zero. But there's a problem: an actual zero is a number, yet
+            // gets left out by this heuristic. So let's also check for the
+            // single, lone zero.
+            if is_alpha_numeric(part) {
+                Identifier::AlphaNumeric(part.to_string())
+            } else {
+                // we can unwrap here because we know it is only digits due to the regex
+                Identifier::Numeric(part.parse().unwrap())
+            }
+        }).collect()
+}
+
+// parse optional metadata (preceded by the prefix character)
+pub fn parse_optional_meta(s: &[u8], prefix_char: u8)-> Result<(Vec<Identifier>, usize), String> {
+    if let Some(len) = prefix_char.p(s) {
+        let start = len;
+        if let Some(len) = letters_numbers_dash_dot(&s[start..]) {
+            let end = start + len;
+            Ok((parse_meta(from_utf8(&s[start..end]).unwrap()), end))
+        } else {
+            Err("Error parsing prerelease".to_string())
+        }
+    } else {
+        Ok((Vec::new(), 0))
+    }
+}
+
+pub fn is_alpha_numeric(s: &str) -> bool {
+    if let Some((_val, len)) = numeric_identifier(s.as_bytes()) {
+        // Return true for number with leading zero
+        // Note: doing it this way also handily makes overflow fail over.
+        len != s.len()
+    } else {
+        true
+    }
+}
+
+// Note: could plumb overflow error up to return value as Result
+pub fn numeric_identifier(s: &[u8]) -> Option<(u64, usize)> {
+    if let Some(len) = Alt(b'0', OneOrMore(Inclusive(b'0'..b'9'))).p(s) {
+        from_utf8(&s[0..len]).unwrap().parse().ok().map(|val| (val, len))
+    } else {
+        None
+    }
+}
+
+pub fn letters_numbers_dash_dot(s: &[u8]) -> Option<usize> {
+    OneOrMore(OneByte(|c| c == b'-' || c == b'.' ||
+        (b'0' <= c && c <= b'9') ||
+        (b'a' <= c && c <= b'z') ||
+        (b'A' <= c && c <= b'Z'))).p(s)
+}