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Decode Kindle FONT container records for AZW3/MOBI font extraction #21

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Decode Kindle FONT container records for AZW3/MOBI font extraction #21

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29 changes: 21 additions & 8 deletions src/import/azw3.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,8 +18,8 @@ use crate::mobi::parser::{
};
use crate::mobi::{
Compression, Encoding, HuffCdicReader, MobiFormat, MobiHeader, NULL_INDEX, PdbInfo, TocNode,
build_toc_from_ncx, detect_image_type, is_metadata_record, palmdoc, parse_exth, parse_fdst,
strip_trailing_data, transform,
build_toc_from_ncx, decode_font_record, detect_font_type, detect_image_type,
is_metadata_record, palmdoc, parse_exth, parse_fdst, strip_trailing_data, transform,
};
use crate::model::{AnchorTarget, Chapter, GlobalNodeId, Landmark, Metadata, TocEntry};

Expand Down Expand Up @@ -155,9 +155,12 @@ impl Importer for Azw3Importer {
fn load_asset(&mut self, path: &Path) -> io::Result<Vec<u8>> {
let key = path.to_string_lossy();

// Parse index from path (images/image_XXXX.ext)
// Parse index from path (images/image_XXXX.ext or fonts/font_XXXX.ext).
// Images and fonts share the same record-index space, so the prefix
// selects naming but the underlying lookup is the same.
let idx: usize = key
.strip_prefix("images/image_")
.or_else(|| key.strip_prefix("fonts/font_"))
.and_then(|s| s.split('.').next())
.and_then(|s| s.parse().ok())
.ok_or_else(|| {
Expand Down Expand Up @@ -582,7 +585,7 @@ impl Azw3Importer {
Ok(cleaned)
}

/// Discover asset paths by scanning image records.
/// Discover asset paths by scanning image and font records.
fn discover_assets(&self) -> Vec<PathBuf> {
let mut assets = Vec::new();

Expand All @@ -592,7 +595,6 @@ impl Azw3Importer {

let first_img = self.mobi.first_image_index as usize + self.record_offset;
for i in first_img..self.pdb.num_records as usize {
// Only read first 16 bytes to detect type (magic bytes)
if let Ok((start, end)) = self.pdb.record_range(i, self.file_len) {
let read_len = 16.min((end - start) as usize);
let mut header = [0u8; 16];
Expand All @@ -605,15 +607,17 @@ impl Azw3Importer {
if is_metadata_record(header) {
continue;
}
let idx = i - first_img;
if let Some(media_type) = detect_image_type(header) {
let ext = match media_type {
"image/jpeg" => "jpg",
"image/png" => "png",
"image/gif" => "gif",
_ => "bin",
};
let idx = i - first_img;
assets.push(PathBuf::from(format!("images/image_{idx:04}.{ext}")));
} else if let Some(font_ext) = detect_font_type(header) {
assets.push(PathBuf::from(format!("fonts/font_{idx:04}.{font_ext}")));
}
}
}
Expand All @@ -622,11 +626,20 @@ impl Azw3Importer {
assets
}

/// Load an image record by index.
/// Load an image or font record by index.
///
/// If the record is a Kindle `FONT` container, it is decoded (XOR + zlib)
/// to extract the raw font bytes. Otherwise the record is returned as-is.
fn load_image_record(&self, idx: usize) -> io::Result<Vec<u8>> {
let first_img = self.mobi.first_image_index as usize + self.record_offset;
let record_idx = first_img + idx;
self.read_record(record_idx)
let data = self.read_record(record_idx)?;

if data.starts_with(b"FONT") {
return decode_font_record(&data);
}

Ok(data)
}

/// Read a record by absolute index.
Expand Down
34 changes: 25 additions & 9 deletions src/import/mobi.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,8 +16,8 @@ use crate::import::{ChapterId, Importer, SpineEntry, resolve_path_based_href};
use crate::io::{ByteSource, FileSource};
use crate::mobi::{
Compression, Encoding, HuffCdicReader, MobiHeader, NULL_INDEX, PdbInfo, TocNode,
build_toc_from_ncx, detect_image_type, filepos, is_metadata_record, palmdoc, parse_exth,
parse_ncx_index, read_index, strip_trailing_data,
build_toc_from_ncx, decode_font_record, detect_font_type, detect_image_type, filepos,
is_metadata_record, palmdoc, parse_exth, parse_ncx_index, read_index, strip_trailing_data,
};
use crate::model::{AnchorTarget, Chapter, GlobalNodeId, Landmark, Metadata, TocEntry};

Expand Down Expand Up @@ -117,9 +117,12 @@ impl Importer for MobiImporter {
fn load_asset(&mut self, path: &Path) -> io::Result<Vec<u8>> {
let key = path.to_string_lossy();

// Parse index from path (images/image_XXXX.ext)
// Parse index from path (images/image_XXXX.ext or fonts/font_XXXX.ext).
// Images and fonts share the same record-index space, so the prefix
// selects naming but the underlying lookup is the same.
let idx: usize = key
.strip_prefix("images/image_")
.or_else(|| key.strip_prefix("fonts/font_"))
.and_then(|s| s.split('.').next())
.and_then(|s| s.parse().ok())
.ok_or_else(|| {
Expand Down Expand Up @@ -339,7 +342,7 @@ impl MobiImporter {
Ok(importer)
}

/// Discover asset paths by scanning image records.
/// Discover asset paths by scanning image and font records.
fn discover_assets(&self) -> Vec<PathBuf> {
let mut assets = Vec::new();

Expand All @@ -361,15 +364,17 @@ impl MobiImporter {
if is_metadata_record(header) {
continue;
}
let idx = i - first_img;
if let Some(media_type) = detect_image_type(header) {
let ext = match media_type {
"image/jpeg" => "jpg",
"image/png" => "png",
"image/gif" => "gif",
_ => "bin",
};
let idx = i - first_img;
assets.push(PathBuf::from(format!("images/image_{idx:04}.{ext}")));
} else if let Some(font_ext) = detect_font_type(header) {
assets.push(PathBuf::from(format!("fonts/font_{idx:04}.{font_ext}")));
}
}
}
Expand All @@ -378,11 +383,20 @@ impl MobiImporter {
assets
}

/// Load an image record by index.
/// Load an image or font record by index.
///
/// If the record is a Kindle `FONT` container, it is decoded (XOR + zlib)
/// to extract the raw font bytes. Otherwise the record is returned as-is.
fn load_image_record(&self, idx: usize) -> io::Result<Vec<u8>> {
let first_img = self.mobi.first_image_index as usize;
let record_idx = first_img + idx;
self.read_record(record_idx)
let data = self.read_record(record_idx)?;

if data.starts_with(b"FONT") {
return decode_font_record(&data);
}

Ok(data)
}

/// Read a record by index.
Expand Down Expand Up @@ -919,7 +933,7 @@ fn is_bare_filename_link(href: &[u8]) -> bool {
// Helpers
// ============================================================================

/// Discover asset paths by scanning image records (standalone function for early use).
/// Discover asset paths by scanning image and font records (standalone function for early use).
fn discover_assets_from_source(
source: &Arc<dyn ByteSource>,
pdb: &PdbInfo,
Expand All @@ -942,15 +956,17 @@ fn discover_assets_from_source(
if is_metadata_record(header) {
continue;
}
let idx = i - first_img;
if let Some(media_type) = detect_image_type(header) {
let ext = match media_type {
"image/jpeg" => "jpg",
"image/png" => "png",
"image/gif" => "gif",
_ => "bin",
};
let idx = i - first_img;
assets.push(PathBuf::from(format!("images/image_{idx:04}.{ext}")));
} else if let Some(font_ext) = detect_font_type(header) {
assets.push(PathBuf::from(format!("fonts/font_{idx:04}.{font_ext}")));
}
}
}
Expand Down
6 changes: 3 additions & 3 deletions src/mobi/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,9 +19,9 @@ pub mod filepos;

pub use parser::{
Compression, Encoding, ExthHeader, HuffCdicReader, MobiFormat, MobiHeader, NULL_INDEX,
NcxEntry, PdbInfo, TocNode, build_toc_from_ncx, detect_font_type, detect_format,
detect_image_type, is_metadata_record, parse_exth, parse_fdst, parse_ncx_index, read_index,
strip_trailing_data,
NcxEntry, PdbInfo, TocNode, build_toc_from_ncx, decode_font_record, detect_font_type,
detect_format, detect_image_type, is_metadata_record, parse_exth, parse_fdst, parse_ncx_index,
read_index, strip_trailing_data,
};

/// Parse Kindle base32 encoding (0-9A-V) to number.
Expand Down
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