specification.md

Specification (Draft)

types

u1/u2/u4/u8: Little-endian unsigned 1/2/4/8 byte(s) integer.

Field:

Field {
  u1 field_id;
  u1[...] field_body;
}

FieldList: A list of fields, ending with the field with field_id 0.

japp file

File format:

JAppFile {
    u4 magic_number; // 0x5050414a ("JAPP")
    u1[...] data_pool;
    BootMetadata boot_metadata;
    LauncherMetadata launcher_metadata;
    FileEnd {
         u4 magic_number; // 0x5050414a ("JAPP")
         u2 major_version;
         u2 minor_version;
         u8 flags;
         u8 file_size;
         u8 boot_metadata_offset;
         u8 launcher_metadata_offset;
         u1[24] reserved;
    } end;
}

boot

BootMetadata:

BootMetadata {
    u4 magic_number; // 0x544f4f42 ("BOOT")
    u4 group_count;
    ByteArrayPool stringsPool;
    ResourceGroup[group_count] groups;
}

ByteArrayPool:

ByteArrayPool {
    u1 magic_number; // 0xf0
    u1 compress_method;
    u2 resvered;
    u4 count;
    u4 uncompressed_bytes_size;
    u4 compressed_bytes_size;
    u2[count] sizes; 
    u1[compressed_length] compressed_bytes;
}

ResourceGroup:

ResourceGroup {
    u1 magic_number; // 0xeb
    u1 compress_method;
    u2 reserved;
    
    u4 uncompressed_size;
    u4 compressed_size;
    u4 resources_count;
    u8 checksum;
    
    u1[compressed_size] compressed_resources;
}

Resource:

Resource {
    u1 magic_number; // 0x1b
    u1 compress_method;
    u2 path_length;
    u4 reserved;
    u8 uncompressed_size;
    u8 compressed_size;
    u8 content_offset;
    u1[path_length] path; // UTF-8  
    
    ResourceFields optional_fields;
}

launcher

LauncherMetadata:

LauncherMetadata {
    ConfigGroup root_group;
}

ConfigGroup:

ConfigGroup {
    u4 magic_number; // 0x00505247 ("GRP\0")
    ConfigGroupFields fields;
}

ResourceGroupReference:

ResourceGroupReference {
    u1 id;
    String name;
    union {
        LocalResourceGroupReference local_reference;
        MavenResourceGroupReference maven_reference;
    } reference;
}

LocalResourceGroupReference {
    
    u4 index;
    u4 multi_count;
    {
        u4 multi_version;
        u4 multi_index;  
    }[multi_count] multi_index_pairs;
}

MavenResourceGroupReference {
    String repository;
    String group;
    String artifact;
    String version;
    String classifier;
}

share

Pass data from launcher to boot launcher: -Dorg.glavo.japp.args=<boot args encoded with base64>

BootArgs {
    String japp_file;
    u8 base_offset;
    u8 boot_metadata_offset;
    u8 boot_metadata_size;
    BootArgFields fields;
}