From b6496c2d20904e665116133a9e9bf9ae6e3b45b8 Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Wed, 2 Feb 2022 04:08:55 -0500
Subject: add internal/cpe

---
 internal/cpe/cpe.go | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 internal/cpe/cpe.go

(limited to 'internal/cpe/cpe.go')

diff --git a/internal/cpe/cpe.go b/internal/cpe/cpe.go
new file mode 100644
index 0000000..73930e8
--- /dev/null
+++ b/internal/cpe/cpe.go
@@ -0,0 +1,94 @@
+// CPE 2.3 formatted string parser.
+//
+// Source: NISTIR 7605, figure 6-3:
+// https://nvlpubs.nist.gov/nistpubs/Legacy/IR/nistir7695.pdf
+package cpe
+
+import (
+  "fmt"
+)
+
+//go:generate stringer -linecomment -type=tokenType
+
+// token type
+type tokenType byte
+
+const (
+  anyToken tokenType = iota // any
+  naToken // na
+  valToken // val
+)
+
+// token
+type token struct {
+  Type tokenType // token type
+  Val string // token value
+}
+
+// parse buffer into token.
+func newToken(val []byte) token {
+  if len(val) > 0 {
+    switch val[0] {
+    case '*':
+      return token { Type: anyToken }
+    case '-':
+      return token { Type: naToken }
+    default:
+      return token { Type: valToken, Val: string(val) }
+    }
+  } else {
+    // empty value
+    return token { Type: valToken, Val: "" }
+  }
+}
+
+// Parse buffer into slice of tokens.
+func tokenize(buf []byte) ([]token, error) {
+  // build result
+  var r []token
+
+  // current token and escape state
+  var curr []byte
+  esc := false
+
+  // build result
+  for _, b := range(buf) {
+    if esc {
+      switch b {
+      // valid escaped characters
+      case '\\', '*', '-', '!', '"', '#', '$', '%', '&', '\'', '(', ')',
+           '+', ',', '/', ':', ';', '<', '=', '>', '@', '[', ']', '^', '`',
+           '{', '|', '}', '~':
+        curr = append(curr, b)
+        esc = false
+      default:
+        return r, fmt.Errorf("invalid escape byte: 0x%02x", b)
+      }
+    } else {
+      switch b {
+      case '\\':
+        esc = true
+      case ':':
+        // push token, clear buffer
+        r = append(r, newToken(curr))
+        curr = nil
+      case 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
+           'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
+           'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+           '-', '.', '_', '*', '?':
+        curr = append(curr, b)
+      default:
+        return r, fmt.Errorf("invalid byte: 0x%02x", b)
+      }
+    }
+  }
+
+  if len(curr) > 0 {
+    // push token, clear buffer
+    r = append(r, newToken(curr))
+    curr = nil
+  }
+
+  // return success
+  return r, nil
+}
-- 
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