Add KOReader XPath sync support for EPUB navigation
Implements bidirectional conversion between KOReader XPath positions and FreeInkBook character offsets. Uses streaming SAX parsing to match chapter text accounting with ChapterLayout, enabling position sync without requiring DOM or pagination. Handles element ancestry tracking, text offset calculation, and spine index extraction.
This commit is contained in:
Justin Mitchell
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#include <gtest/gtest.h>
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#include <cstring>
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#include <string>
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#include <vector>
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#include "BookXPath.h"
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// ============================================================================
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// In-memory stored-ZIP fixture: BookXPath streams chapters through the
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// engine's ZipEntryReader, which reads the entry's local file header first,
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// so the buffer must be a structurally valid (uncompressed) zip member.
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// ============================================================================
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namespace {
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using freeink::book::BookSource;
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using freeink::book::ZipCatalog;
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using freeink::book::ZipEntry;
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class MemorySource : public BookSource {
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public:
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explicit MemorySource(std::vector<uint8_t> bytes) : bytes_(std::move(bytes)) {}
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int32_t readAt(uint64_t offset, void* dst, uint32_t len) override {
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if (offset >= bytes_.size()) return 0;
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const uint32_t n = std::min<uint64_t>(len, bytes_.size() - offset);
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memcpy(dst, bytes_.data() + offset, n);
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return static_cast<int32_t>(n);
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}
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uint64_t size() const override { return bytes_.size(); }
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private:
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std::vector<uint8_t> bytes_;
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};
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void putU16(std::vector<uint8_t>& v, uint16_t x) {
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v.push_back(x & 0xFF);
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v.push_back(x >> 8);
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}
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void putU32(std::vector<uint8_t>& v, uint32_t x) {
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for (int i = 0; i < 4; ++i) v.push_back((x >> (8 * i)) & 0xFF);
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}
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// One stored (method 0) zip member at offset 0, plus the matching ZipEntry.
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struct Fixture {
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MemorySource source;
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ZipEntry entry;
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ZipCatalog zip; // unused by BookXPath but part of its signature
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static Fixture fromXhtml(const std::string& xhtml) {
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std::vector<uint8_t> buf;
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const char* name = "ch.xhtml";
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putU32(buf, 0x04034b50); // local file header signature
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putU16(buf, 20); // version needed
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putU16(buf, 0); // flags
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putU16(buf, 0); // method: stored
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putU16(buf, 0); // mod time
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putU16(buf, 0); // mod date
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putU32(buf, 0); // crc-32 (not validated on stored reads)
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putU32(buf, static_cast<uint32_t>(xhtml.size())); // compressed size
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putU32(buf, static_cast<uint32_t>(xhtml.size())); // uncompressed size
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putU16(buf, static_cast<uint16_t>(strlen(name))); // name length
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putU16(buf, 0); // extra length
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buf.insert(buf.end(), name, name + strlen(name));
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buf.insert(buf.end(), xhtml.begin(), xhtml.end());
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Fixture f{MemorySource(std::move(buf)), ZipEntry{}, ZipCatalog{}};
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f.entry.name = "ch.xhtml";
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f.entry.method = 0;
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f.entry.compressedSize = static_cast<uint32_t>(xhtml.size());
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f.entry.uncompressedSize = static_cast<uint32_t>(xhtml.size());
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f.entry.localHeaderOffset = 0;
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return f;
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}
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};
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// Character accounting reference for kChapter (mirrors ChapterLayout):
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// p1 "Hello world" chars 0..10
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// p2 "Second para here" chars 11..26
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// p3 "Third" chars 27..31
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const char kChapter[] =
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"<?xml version=\"1.0\"?>"
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"<html xmlns=\"http://www.w3.org/1999/xhtml\">"
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"<head><title>Ignored Title</title><style>p { color: red; }</style></head>"
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"<body>"
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"<div><p>Hello world</p><p>Second <i>para</i> here</p></div>"
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"<p>Third</p>"
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"</body></html>";
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} // namespace
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TEST(BookXPath, SpineIndexFromXpath) {
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EXPECT_EQ(BookXPath::spineIndexForXpath("/body/DocFragment[8]/body/p[4]/text().96"), 7);
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EXPECT_EQ(BookXPath::spineIndexForXpath("/body/DocFragment[1]"), 0);
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EXPECT_EQ(BookXPath::spineIndexForXpath("/body/nope"), -1);
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EXPECT_EQ(BookXPath::spineIndexForXpath(""), -1);
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}
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TEST(BookXPath, CharStartToXpathRealAncestry) {
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auto f = Fixture::fromXhtml(kChapter);
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// Char 0: first char of p1 inside the div.
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EXPECT_EQ(BookXPath::xpathForCharStart(f.source, f.zip, f.entry, 2, 0),
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"/body/DocFragment[3]/body/div[1]/p[1]/text().0");
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// Char 13 = "cond..." — 3rd char (offset 2) of p2. Whitespace in p1
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// ("Hello world") must have collapsed to a single space for this to hold.
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EXPECT_EQ(BookXPath::xpathForCharStart(f.source, f.zip, f.entry, 2, 13),
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"/body/DocFragment[3]/body/div[1]/p[2]/text().2");
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// Char 28 = 2nd char of p3 — body's FIRST p child (div doesn't count:
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// sibling indices are per-tag).
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EXPECT_EQ(BookXPath::xpathForCharStart(f.source, f.zip, f.entry, 2, 28),
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"/body/DocFragment[3]/body/p[1]/text().1");
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// Past the end of the chapter: chapter-level fallback.
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EXPECT_EQ(BookXPath::xpathForCharStart(f.source, f.zip, f.entry, 2, 100000), "/body/DocFragment[3]");
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}
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TEST(BookXPath, XpathToCharStartRoundTrip) {
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auto f = Fixture::fromXhtml(kChapter);
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uint32_t ch = 0;
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ASSERT_TRUE(BookXPath::charStartForXpath(f.source, f.zip, f.entry,
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"/body/DocFragment[3]/body/div[1]/p[2]/text().2", &ch));
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EXPECT_EQ(ch, 13u);
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ASSERT_TRUE(
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BookXPath::charStartForXpath(f.source, f.zip, f.entry, "/body/DocFragment[3]/body/p[1]/text().1", &ch));
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EXPECT_EQ(ch, 28u);
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// Elements without an explicit index default to [1].
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ASSERT_TRUE(
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BookXPath::charStartForXpath(f.source, f.zip, f.entry, "/body/DocFragment[3]/body/div/p[1]/text().5", &ch));
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EXPECT_EQ(ch, 5u);
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// Chapter-level xpath resolves to the chapter start.
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ASSERT_TRUE(BookXPath::charStartForXpath(f.source, f.zip, f.entry, "/body/DocFragment[3]", &ch));
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EXPECT_EQ(ch, 0u);
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// Ancestry that does not exist in the chapter.
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EXPECT_FALSE(BookXPath::charStartForXpath(f.source, f.zip, f.entry,
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"/body/DocFragment[3]/body/section[2]/p[9]/text().0", &ch));
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}
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TEST(BookXPath, InlineElementTargetsResolve) {
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auto f = Fixture::fromXhtml(kChapter);
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// KOReader may point inside an inline element: <i>para</i> starts at
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// char 18 ("Second " = 7 chars into p2, which starts at 11).
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uint32_t ch = 0;
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ASSERT_TRUE(BookXPath::charStartForXpath(f.source, f.zip, f.entry,
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"/body/DocFragment[3]/body/div[1]/p[2]/i[1]/text().0", &ch));
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EXPECT_EQ(ch, 18u);
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}
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TEST(BookXPath, EntitiesAndBrAccounting) {
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// "A&B" is 3 chars; <br/> contributes one '\n' char (layout parity).
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auto f = Fixture::fromXhtml(
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"<html><body><p>A&B<br/>C</p></body></html>");
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EXPECT_EQ(BookXPath::xpathForCharStart(f.source, f.zip, f.entry, 0, 4),
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"/body/DocFragment[1]/body/p[1]/text().4"); // 'C' after A,&,B,\n
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uint32_t ch = 0;
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ASSERT_TRUE(BookXPath::charStartForXpath(f.source, f.zip, f.entry, "/body/DocFragment[1]/body/p[1]/text().4", &ch));
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EXPECT_EQ(ch, 4u);
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}
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