From 8e657a341776c5e8cdc8596021d50935e9228262 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Thu, 12 Sep 2024 17:11:35 +0530
Subject: [PATCH] Start work on speeding up HTML entity replacement

---
 setup/extensions.json                |   7 ++
 src/calibre/constants.py             |   1 +
 src/calibre/ebooks/html_entities.cpp | 126 +++++++++++++++++++++++++++
 3 files changed, 134 insertions(+)
 create mode 100644 src/calibre/ebooks/html_entities.cpp

diff --git a/setup/extensions.json b/setup/extensions.json
index 4e0c7cdf4c..7a3f7895bc 100644
--- a/setup/extensions.json
+++ b/setup/extensions.json
@@ -138,6 +138,13 @@
 		"inc_dirs": "perfect-hashing",
 		"needs_c++": "14"
     },
+    {
+        "name": "fast_html_entities",
+        "headers": "calibre/utils/cpp_binding.h calibre/utils/stb_sprintf.h",
+        "sources": "calibre/ebooks/html_entities.cpp",
+		"inc_dirs": "perfect-hashing",
+		"needs_c++": "14"
+    },
     {
         "name": "rcc_backend",
         "sources": "calibre/utils/rcc/rcc.cpp",
diff --git a/src/calibre/constants.py b/src/calibre/constants.py
index 6f8c8398a5..4295ad588f 100644
--- a/src/calibre/constants.py
+++ b/src/calibre/constants.py
@@ -260,6 +260,7 @@ class ExtensionsImporter:
             'speedup',
             'html_as_json',
             'fast_css_transform',
+            'fast_html_entities',
             'unicode_names',
             'html_syntax_highlighter',
             'hyphen',
diff --git a/src/calibre/ebooks/html_entities.cpp b/src/calibre/ebooks/html_entities.cpp
new file mode 100644
index 0000000000..4fb5d085f4
--- /dev/null
+++ b/src/calibre/ebooks/html_entities.cpp
@@ -0,0 +1,126 @@
+/*
+ * html_entities.cpp
+ * Copyright (C) 2024 Kovid Goyal <kovid at kovidgoyal.net>
+ *
+ * Distributed under terms of the GPL3 license.
+ */
+
+#define PY_SSIZE_T_CLEAN
+#define UNICODE
+#define _UNICODE
+#include <Python.h>
+#include <frozen/unordered_map.h>
+#include <frozen/string.h>
+#include "../utils/cpp_binding.h"
+
+static size_t
+add_entity(const char *entity, size_t elen, char *output) {
+    size_t ans = 0;
+    char e[64];
+    if (elen > sizeof(e) - 1) {
+        output[ans++] = '&';
+        memcpy(output + ans, entity, elen);
+        ans += elen;
+        output[ans++] = ';';
+        return ans;
+    }
+    if (!elen) {
+        output[ans++] = '&';
+        output[ans++] = ';';
+        return ans;
+    }
+    memcpy(e, entity, elen);
+    e[elen] = 0;
+
+    return 0;
+}
+
+
+static size_t
+process_entity(const char *input, size_t input_sz, char *output, size_t *output_pos) {
+    size_t input_pos = 0;
+    while (input_pos < input_sz) {
+        char ch = input[input_pos++];
+        switch (ch) {
+            case 'a' ... 'z': case 'A' ... 'Z': case '0' ... '9': case '#': case '_': case '-': case '+':
+                break;
+            case ';':
+                *output_pos += add_entity(input, input_pos-1, output + *output_pos);
+                break;
+            default:
+                output[(*output_pos)++] = '&';
+                memcpy(output + *output_pos, input, input_pos);
+                *output_pos += input_pos;
+                break;
+        }
+    }
+    return input_pos;
+}
+
+static size_t
+replace(const char *input, size_t input_sz, char *output, int keep_xml_entities) {
+    size_t input_pos = 0, output_pos = 0;
+    while (input_pos < input_sz) {
+        const char *p = (const char*)memchr(input + input_pos, '&', input_sz - input_pos);
+        if (p) {
+            if (p > input + input_pos) {
+                size_t sz = p - (input + input_pos);
+                memcpy(output + output_pos, input + input_pos, sz);
+                output_pos += sz;
+                input_pos += sz;
+            }
+            input_pos += process_entity(p, input_sz - (p - input), output, &output_pos);
+        } else {
+            memcpy(output + output_pos, input + input_pos, input_sz - input_pos);
+            output_pos += input_sz - input_pos;
+            input_pos = input_sz;
+        }
+    }
+    return output_pos;
+}
+
+static PyObject*
+replace_entities(PyObject *self, PyObject *const *args, Py_ssize_t nargs) {
+    if (nargs < 1) { PyErr_SetString(PyExc_TypeError, "Must specify string tp process"); return NULL; }
+    const char *input = NULL; Py_ssize_t input_sz = 0;
+    int keep_xml_entities = false;
+    if (PyUnicode_Check(args[0])) {
+        input = PyUnicode_AsUTF8AndSize(args[0], &input_sz);
+        if (!input) return NULL;
+    } else if (PyBytes_Check(args[0])) {
+        input = PyBytes_AS_STRING(args[0]); input_sz = PyBytes_GET_SIZE(args[0]);
+    } else {
+        PyErr_SetString(PyExc_TypeError, "string must be unicode object or UTF-8 encoded bytes"); return NULL;
+    }
+    if (nargs > 1) keep_xml_entities = PyObject_IsTrue(args[1]);
+    generic_raii<char*, pymem_free> output((char*)PyMem_Malloc(input_sz + 1));
+    if (!output) { return PyErr_NoMemory(); }
+    size_t output_sz = replace(input, input_sz, output.ptr(), keep_xml_entities);
+    if (PyErr_Occurred()) return NULL;
+    if (!output_sz) return Py_NewRef(args[0]);
+    if (PyUnicode_Check(args[0])) return PyUnicode_FromStringAndSize(output.ptr(), output_sz);
+    return PyBytes_FromStringAndSize(output.ptr(), output_sz);
+}
+
+static PyMethodDef methods[] = {
+    {"replace_entities", (PyCFunction)replace_entities, METH_FASTCALL,
+     "Replace entities in the specified string"
+    },
+    {NULL, NULL, 0, NULL}
+};
+
+static int
+exec_module(PyObject *m) {
+    return 0;
+}
+
+CALIBRE_MODINIT_FUNC PyInit_fast_html_entities(void) {
+    static PyModuleDef_Slot slots[] = { {Py_mod_exec, (void*)exec_module}, {0, NULL} };
+    static struct PyModuleDef module_def = {PyModuleDef_HEAD_INIT};
+
+    module_def.m_name     = "fast_html_entities";
+    module_def.m_doc      = "Fast conversion of HTML entities";
+    module_def.m_methods  = methods;
+    module_def.m_slots    = slots;
+	return PyModuleDef_Init(&module_def);
+}