feat: add utility functions for environment variable handling, file operations, pointer manipulation, random generation, and string processing

utils/randx/randx.go

@@ -0,0 +1,77 @@
+package randx
+
+import (
+    crand "crypto/rand"
+    "encoding/hex"
+    "io"
+)
+
+// Bytes returns n cryptographically secure random bytes.
+func Bytes(n int) ([]byte, error) {
+    if n <= 0 {
+        return []byte{}, nil
+    }
+    b := make([]byte, n)
+    _, err := io.ReadFull(crand.Reader, b)
+    return b, err
+}
+
+var urlSafe = []byte("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_")
+
+// String returns a URL-safe random string of length n using a cryptographically secure source.
+func String(n int) (string, error) {
+    if n <= 0 {
+        return "", nil
+    }
+    out := make([]byte, n)
+    // rejection sampling to avoid modulo bias
+    // we want uniform selection from urlSafe (len m)
+    m := len(urlSafe)
+    threshold := 256 - (256 % m)
+    var buf [1]byte
+    for i := 0; i < n; i++ {
+        for {
+            if _, err := io.ReadFull(crand.Reader, buf[:]); err != nil {
+                return "", err
+            }
+            b := int(buf[0])
+            if b < threshold {
+                out[i] = urlSafe[b%m]
+                break
+            }
+        }
+    }
+    return string(out), nil
+}
+
+// MustString is like String but panics on error.
+func MustString(n int) string {
+    s, err := String(n)
+    if err != nil {
+        panic(err)
+    }
+    return s
+}
+
+// UUIDv4 generates a RFC 4122 version 4 UUID string.
+func UUIDv4() (string, error) {
+    b := make([]byte, 16)
+    if _, err := io.ReadFull(crand.Reader, b); err != nil {
+        return "", err
+    }
+    // Set version (4) and variant (10)
+    b[6] = (b[6] & 0x0f) | 0x40
+    b[8] = (b[8] & 0x3f) | 0x80
+    // Format 8-4-4-4-12
+    dst := make([]byte, 36)
+    hex.Encode(dst[0:8], b[0:4])
+    dst[8] = '-'
+    hex.Encode(dst[9:13], b[4:6])
+    dst[13] = '-'
+    hex.Encode(dst[14:18], b[6:8])
+    dst[18] = '-'
+    hex.Encode(dst[19:23], b[8:10])
+    dst[23] = '-'
+    hex.Encode(dst[24:36], b[10:16])
+    return string(dst), nil
+}