1 files changed, 131 insertions, 0 deletions
diff --git a/nvdmirror/jsoncache.go b/nvdmirror/jsoncache.go
new file mode 100644
index 0000000..7e84a94
--- /dev/null
+++ b/nvdmirror/jsoncache.go
@@ -0,0 +1,131 @@
+package nvdmirror
+
+import (
+  "compress/gzip"
+  "encoding/json"
+  "os"
+  "path/filepath"
+  "time"
+)
+
+// JSON file backed URL cache.
+type JsonCache struct {
+  dirty bool // has the cache been modified?
+  path string // backing JSON file
+  vals map[string]Entry // entries
+}
+
+// Create new JSON cache.
+func NewJsonCache(path string) (JsonCache, error) {
+  r := JsonCache {
+    path: path,
+  }
+
+  // open path
+  f, err := os.OpenFile(path, os.O_CREATE, 0640)
+  if err != nil {
+    return r, err
+  }
+  defer f.Close()
+
+  // stat file
+  st, err := f.Stat()
+  if err != nil {
+    return r, err
+  }
+
+  vals := make(map[string]Entry)
+  if st.Size() > 0 {
+    // create gzip reader
+    zr, err := gzip.NewReader(f)
+    if err != nil {
+      return r, err
+    }
+
+    // read/decode json
+    d := json.NewDecoder(zr)
+    if err := d.Decode(&vals); err != nil {
+      return r, err
+    }
+  }
+
+  // save path and values
+  r.path = path
+  r.vals = vals
+
+  // return success
+  return r, nil
+}
+
+// Get cache entry
+func (me JsonCache) Get(s string) (map[string]string, bool) {
+  if e, ok := me.vals[s]; ok {
+    return e.Headers, ok
+  } else {
+    return nil, false
+  }
+}
+
+// Set cache entry.
+func (me *JsonCache) Set(s string, headers map[string]string) error {
+  // mark cache as dirty
+  me.dirty = true
+
+  // copy map to internal storage
+  newHeaders := make(map[string]string)
+  for k, v := range(headers) {
+    newHeaders[k] = v
+  }
+
+  // update entry
+  me.vals[s] = Entry {
+    Time: time.Now(),
+    Headers: newHeaders,
+  }
+
+  // return success
+  return nil
+}
+
+// Remove cache entry, if it exists.
+func (me *JsonCache) Delete(s string) error {
+  me.dirty = true
+  delete(me.vals, s)
+  return nil
+}
+
+// Save and close cache.
+func (me *JsonCache) Close() error {
+  if !me.dirty {
+    // return success
+    return nil
+  }
+
+  // open temp output file
+  t, err := os.CreateTemp(filepath.Dir(me.path), "")
+  if err != nil {
+    return err
+  }
+  defer os.Remove(t.Name())
+
+  // encode/compress JSON
+  zw := gzip.NewWriter(t)
+  e := json.NewEncoder(zw)
+  if err = e.Encode(me.vals); err != nil {
+    return err
+  }
+
+  // flush changes
+  if err = zw.Flush(); err != nil {
+    return err
+  }
+
+  // rename to destination file
+  if err = os.Rename(t.Name(), me.path); err != nil {
+    return err
+  }
+
+  // Mark cache as clean, return success.
+  me.dirty = false
+  return nil
+}