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const std = @import("std");
const type_details: []const struct {
typ: FileType,
sigs: []const []const ?u8,
exts: []const []const u8,
} = &.{
.{
.typ = .jpeg,
.sigs = &.{
&.{ 0xFF, 0xD8, 0xFF, 0xDB },
&.{ 0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10, 0x4A, 0x46, 0x49, 0x46, 0x00, 0x01 },
&.{ 0xFF, 0xD8, 0xFF, 0xEE },
&.{ 0xFF, 0xD8, 0xFF, 0xE1, null, null, 0x45, 0x78, 0x69, 0x66, 0x00, 0x00 },
&.{ 0xFF, 0xD8, 0xFF, 0xE0 },
},
.exts = &.{ ".jpg", ".jpeg", ".jfif" },
},
.{
.typ = .png,
.sigs = &.{&.{ 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A }},
.exts = &.{".png"},
},
.{
.typ = .gif,
.sigs = &.{
&.{ 'G', 'I', 'F', '8', '7', 'a' },
&.{ 'G', 'I', 'F', '8', '9', 'a' },
},
.exts = &.{".gif"},
},
.{
.typ = .bmp,
.sigs = &.{&.{ 'B', 'M' }},
.exts = &.{".bmp"},
},
.{
.typ = .qoi,
.sigs = &.{&.{ 'q', 'o', 'i', 'f' }},
.exts = &.{".qoi"},
},
.{
.typ = .webp,
.sigs = &.{
&.{ 0x52, 0x49, 0x46, 0x46, null, null, null, null, 0x57, 0x45, 0x42, 0x50 },
},
.exts = &.{".webp"},
},
};
/// This is a helper for detecting file types based on magic bytes.
///
/// Ref: https://en.wikipedia.org/wiki/List_of_file_signatures
pub const FileType = enum {
/// JPEG image file.
jpeg,
/// PNG image file.
png,
/// GIF image file.
gif,
/// BMP image file.
bmp,
/// QOI image file.
qoi,
/// WebP image file.
webp,
/// Unknown file format.
unknown,
/// Detect file type based on the magic bytes
/// at the start of the provided file contents.
pub fn detect(contents: []const u8) FileType {
inline for (type_details) |typ| {
inline for (typ.sigs) |signature| {
if (contents.len >= signature.len) {
for (contents[0..signature.len], signature) |f, sig| {
if (sig) |s| if (f != s) break;
} else {
return typ.typ;
}
}
}
}
return .unknown;
}
/// Guess file type from its extension.
pub fn guessFromExtension(extension: []const u8) FileType {
inline for (type_details) |typ| {
inline for (typ.exts) |ext| {
if (std.ascii.eqlIgnoreCase(extension, ext)) return typ.typ;
}
}
return .unknown;
}
};
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