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// EXIF 元数据写入（纯 MoonBit）
// 支持将 ExifInfo 写入 JPEG 字节流
///|
fn write_u16_be(buf : Array[Byte], val : Int) -> Unit {
buf.push(((val >> 8) & 0xFF).to_byte())
buf.push((val & 0xFF).to_byte())
}
///|
fn write_u32_be(buf : Array[Byte], val : Int) -> Unit {
buf.push(((val >> 24) & 0xFF).to_byte())
buf.push(((val >> 16) & 0xFF).to_byte())
buf.push(((val >> 8) & 0xFF).to_byte())
buf.push((val & 0xFF).to_byte())
}
///|
fn string_to_exif_bytes(s : String) -> Bytes {
let buf : Array[Byte] = []
for c in s.to_array() {
let code = c.to_int()
if code < 128 {
buf.push(code.to_byte())
} else {
buf.push(b'?')
}
}
buf.push(b'\x00')
Bytes::from_array(buf)
}
///|
/// 构造 EXIF APP1 segment 数据（不含 FF E1 前缀和长度）。
/// 返回 "Exif\0\0" + TIFF 头(大端) + IFD0 + 数据区
pub fn create_exif_segment(info : ExifInfo) -> Bytes {
let make_bytes = string_to_exif_bytes(info.make)
let model_bytes = string_to_exif_bytes(info.model)
let dt_bytes = string_to_exif_bytes(info.date_time)
let make_count = make_bytes.length()
let model_count = model_bytes.length()
let dt_count = dt_bytes.length()
let entry_count = 4
let ifd0_size = 2 + entry_count * 12 + 4
let data_start = 8 + ifd0_size
let mut offset = data_start
let make_offset = if make_count <= 4 {
-1
} else {
let o = offset
offset += make_count
o
}
let model_offset = if model_count <= 4 {
-1
} else {
let o = offset
offset += model_count
o
}
let dt_offset = if dt_count <= 4 {
-1
} else {
let o = offset
offset += dt_count
o
}
let buf : Array[Byte] = []
buf.push(b'E')
buf.push(b'x')
buf.push(b'i')
buf.push(b'f')
buf.push(b'\x00')
buf.push(b'\x00')
buf.push(b'M')
buf.push(b'M')
buf.push(b'\x00')
buf.push(b'\x2A')
buf.push(b'\x00')
buf.push(b'\x00')
buf.push(b'\x00')
buf.push(b'\x08')
write_u16_be(buf, entry_count)
write_u16_be(buf, 0x010F)
write_u16_be(buf, 2)
write_u32_be(buf, make_count)
if make_count <= 4 {
for j in 0..<make_count {
buf.push(make_bytes[j])
}
for _ in make_count..<4 {
buf.push(b'\x00')
}
} else {
write_u32_be(buf, make_offset)
}
write_u16_be(buf, 0x0110)
write_u16_be(buf, 2)
write_u32_be(buf, model_count)
if model_count <= 4 {
for j in 0..<model_count {
buf.push(model_bytes[j])
}
for _ in model_count..<4 {
buf.push(b'\x00')
}
} else {
write_u32_be(buf, model_offset)
}
write_u16_be(buf, 0x0112)
write_u16_be(buf, 3)
write_u32_be(buf, 1)
write_u16_be(buf, info.orientation)
buf.push(b'\x00')
buf.push(b'\x00')
write_u16_be(buf, 0x0132)
write_u16_be(buf, 2)
write_u32_be(buf, dt_count)
if dt_count <= 4 {
for j in 0..<dt_count {
buf.push(dt_bytes[j])
}
for _ in dt_count..<4 {
buf.push(b'\x00')
}
} else {
write_u32_be(buf, dt_offset)
}
write_u32_be(buf, 0)
if make_count > 4 {
for j in 0..<make_count {
buf.push(make_bytes[j])
}
}
if model_count > 4 {
for j in 0..<model_count {
buf.push(model_bytes[j])
}
}
if dt_count > 4 {
for j in 0..<dt_count {
buf.push(dt_bytes[j])
}
}
Bytes::from_array(buf)
}
///|
/// 将 EXIF 元数据写入 JPEG 字节流。
/// 在 SOI (FF D8) 之后插入 APP1 segment。
/// 如果已有 APP1 EXIF segment，替换之。
pub fn write_exif_to_bytes(
info : ExifInfo,
jpeg_data : Bytes,
) -> Bytes raise @types.LoadError {
let len = jpeg_data.length()
if len < 2 || jpeg_data[0].to_int() != 0xFF || jpeg_data[1].to_int() != 0xD8 {
raise @types.LoadError::DecodeFailed("Not a valid JPEG: missing SOI marker")
}
let exif_data = create_exif_segment(info)
let exif_len = exif_data.length()
let app1_size = exif_len + 2
let mut pos = 2
let mut existing_app1_end = -1
while pos < len - 1 {
if jpeg_data[pos].to_int() == 0xFF {
let marker = jpeg_data[pos + 1].to_int()
if marker == 0xE1 {
let seg_len = jpeg_data[pos + 2].to_int() * 256 +
jpeg_data[pos + 3].to_int()
existing_app1_end = pos + 2 + seg_len
break
}
if marker == 0xDA || marker == 0xD9 {
break
}
if marker == 0x00 || (marker >= 0xD0 && marker <= 0xD7) {
pos += 2
} else {
let seg_len = jpeg_data[pos + 2].to_int() * 256 +
jpeg_data[pos + 3].to_int()
pos += 2 + seg_len
}
} else {
pos += 1
}
}
let result : Array[Byte] = []
result.push(b'\xFF')
result.push(b'\xD8')
result.push(b'\xFF')
result.push(b'\xE1')
write_u16_be(result, app1_size)
for i in 0..<exif_len {
result.push(exif_data[i])
}
let rest_start = if existing_app1_end >= 0 { existing_app1_end } else { 2 }
for i in rest_start..<len {
result.push(jpeg_data[i])
}
Bytes::from_array(result)
}