fixes #942

Author: jph00

fastcore/editskill.py

@@ -50,7 +50,7 @@
 
 Prefer lnhash addresses when `exhash` is installed. The editor checks the hash against current content and rejects stale addresses. Plain line numbers are unverified and can shift after an edit. Re-view after each plain-line-number edit and apply multiple edits from bottom to top. Read `exhash.skill` for address formats and verified editing.
 
-Section tokens identify sections in document outlines. In `1.6.|12|a3f2|,45|b1c3|`, `1.6.` is the section number. The rest is the lnhash range for its first and last lines. `d.at(token)` returns the section after checking its hash. `d.view(tok1, tok2)` prints the rendered text of both sections. Use the boundary range to edit the section: `file_exhash(path, ('12|a3f2|,45|b1c3|', 'c', new_text))`.
+Section tokens identify sections in document outlines. In `1.6.|12|Py|,45|HD|`, `1.6.` is the section number. The rest is the lnhash range for its first and last lines. `d.at(token)` returns the section after checking its hash. `d.view(tok1, tok2)` prints the rendered text of both sections. Use the boundary range to edit the section: `file_exhash(path, ('12|Py|,45|HD|', 'c', new_text))`.
 
 Read `exhash.skill` before working through large Markdown, code, or notebook files, or documentation from a URL. It describes `open_doc` tree searches and link following, including the llms.txt workflow.
 

fastcore/tools.py

@@ -4,7 +4,7 @@
 
 Read `fastcore.editskill` for the editing toolkit's naming, parameter and workflow conventions. It exposes these tools alongside the notebook editors from `fastcore.nbio`.
 
-`line_hash`, `lnhash` and `lnhash_at` create [exhash](https://answerdotai.github.io/exhash) addresses without depending on the exhash package. Addresses use `lineno|hash|`. The hash is the low 16 bits of CRC32, formatted as four hexadecimal characters.
+`line_hash`, `lnhash` and `lnhash_at` create [exhash](https://answerdotai.github.io/exhash) addresses without depending on the exhash package. Addresses use `lineno|hash|`. The hash is the low 12 bits of CRC32, encoded as two Base64url characters (`A–Z`, `a–z`, `0–9`, `-`, `_`), high six bits first.
 
 File editors take the path first and return a unified diff. An unchanged result returns `none: No changes.` Invalid edits return `error: ...`.
 
@@ -152,8 +152,10 @@ def del_lines(
 def line_hash(
     line:str # Text to hash; when hashing a single line, omit its trailing newline
 )->str:
-    "4-char hex hash of `line`"
-    return f'{zlib.crc32(line.encode()) & 0xffff:04x}'
+    "2-char Base64url hash of `line`"
+    alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_'
+    h = zlib.crc32(line.encode())
+    return alphabet[(h>>6)&63] + alphabet[h&63]
 
 def lnhash(
     lineno:int, # 1-based line number

nbs/12_tools.ipynb

@@ -186,7 +186,18 @@
    "execution_count": null,
    "id": "8079ef9d",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'a-b\\nb a'"
+      ]
+     },
+     "execution_count": null,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "res = str_replace('keep q\\nfix q\\nkeep q', 'q', 'y', re_filter='fix')\n",
     "test_eq(res, 'keep q\\nfix y\\nkeep q')\n",
@@ -371,7 +382,7 @@
    "metadata": {},
    "source": [
     "#| export\n",
-    "`line_hash`, `lnhash` and `lnhash_at` create [exhash](https://answerdotai.github.io/exhash) addresses without depending on the exhash package. Addresses use `lineno|hash|`. The hash is the low 16 bits of CRC32, formatted as four hexadecimal characters."
+    "`line_hash`, `lnhash` and `lnhash_at` create [exhash](https://answerdotai.github.io/exhash) addresses without depending on the exhash package. Addresses use `lineno|hash|`. The hash is the low 12 bits of CRC32, encoded as two Base64url characters (`A–Z`, `a–z`, `0–9`, `-`, `_`), high six bits first."
    ]
   },
   {
@@ -385,8 +396,10 @@
     "def line_hash(\n",
     "    line:str # Text to hash; when hashing a single line, omit its trailing newline\n",
     ")->str:\n",
-    "    \"4-char hex hash of `line`\"\n",
-    "    return f'{zlib.crc32(line.encode()) & 0xffff:04x}'\n",
+    "    \"2-char Base64url hash of `line`\"\n",
+    "    alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_'\n",
+    "    h = zlib.crc32(line.encode())\n",
+    "    return alphabet[(h>>6)&63] + alphabet[h&63]\n",
     "\n",
     "def lnhash(\n",
     "    lineno:int, # 1-based line number\n",
@@ -413,7 +426,7 @@
     {
      "data": {
       "text/plain": [
-       "'2|54f0|'"
+       "'2|Tw|'"
       ]
      },
      "execution_count": null,
@@ -422,10 +435,10 @@
     }
    ],
    "source": [
-    "test_eq(line_hash('def foo(): pass'), '54f0')  # same value the exhash Rust impl produces\n",
+    "test_eq(line_hash('def foo(): pass'), 'Tw')  # same value the exhash Rust impl produces\n",
     "s = 'a\\ndef foo(): pass\\nb'\n",
-    "test_eq(lnhash_at(s, 2), '2|54f0|')\n",
-    "test_eq(lnhash_at(s.splitlines(), 2), '2|54f0|')\n",
+    "test_eq(lnhash_at(s, 2), '2|Tw|')\n",
+    "test_eq(lnhash_at(s.splitlines(), 2), '2|Tw|')\n",
     "test_eq(lnhash_at(s, 2), lnhash(2, 'def foo(): pass'))\n",
     "lnhash_at(s, 2)"
    ]
@@ -493,7 +506,7 @@
     {
      "data": {
       "text/plain": [
-       "'/var/folders/51/b2_szf2945n072c0vj2cyty40000gn/T/tmpaax7zfjh/test.txt'"
+       "'/var/folders/mv/nt5dfl8j0xbg7zkfw_sk_d8m0000gn/T/tmpxaep7ttt/test.txt'"
       ]
      },
      "execution_count": null,
@@ -542,8 +555,8 @@
     {
      "data": {
       "text/plain": [
-       "2|0463|beta\n",
-       "3|d071|gamma"
+       "2|Rj|beta\n",
+       "3|Bx|gamma"
       ]
      },
      "execution_count": null,