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  1. this is just a draft, feel free to suggest whatever. Abstract This document describes the URF, intended to make mass file exchange easier. Rationale There are many competing methods of exchanging large amounts of files, and many are incomplete, such as TAR implementations, or proprietary, such as NeoPAKv1. With this in mind, a standard format will make file exchange less error prone. Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. All integers are unsigned arbitrary length integers as specified in the Document, unless otherwise specified. All strings are encoded with UTF-8, prepended with an integer corresponding to the length of the string in bytes. Character specifications such as NULL and DC1 are part of US ASCII, unless otherwise specified. Concepts Signature: Data at the beginning of the File, marking the File as a URF format archive, and specifying the version. File Table: Data structure containing all file information. Entry: Any data sub-structure in the File Table. Entry Specifier byte: A byte describing how to decode the data contained in an Entry. Object: A filesystem structure, i.e.. "file" or "directory". Attributes: Data describing the size, offset, parent Object, and Object ID of an Object. Extended Attributes: Data describing non-core attributes such as Permissions, Owner, Security, etc. Producer: A program or process that generates data in this format. Consumer: A program or process that consumes data in this format. Arbitrary length integers Arbitrary length integers (ALIs) MAY be over 64-bits in precision. ALIs are little endian. For each byte, add the value of the first seven bits, shifted by 7 times the number of characters currently read bits, to the the read value and repeat until the 8th bit is 0. Signature The Signature MUST be URF followed by a DC1 character, or an unsigned 32-bit little endian integer equal to 1431455249. The next two bytes MUST be the version number, the first being the major version, the second being the minor version. The next two bytes MUST be DC2 followed by a NULL character. File Table The File Table MUST start after the Signature. This MUST contain all Entries, and MUST end with an EOH Entry. See EOH Entry. Entry An Entry MUST start with an Entry Specifier byte. The Entry Specifier byte MUST be followed with an integer specifying the length. Data contained SHOULD be skipped if the Entry Specifier byte allows and the Entry Type is not understood. Entry Specifier byte An Entry Specifier byte MUST have the 7th bit set to 1. If the Consumer comes across an entry with the 7th bit not set to 1, the Consumer MUST stop reading the file and raise a fatal error. The 6th byte specifies if the entry is critical. If the entry is critical and not understood, the Consumer should raise a fatal error; if the entry is non-critical, the Consumer SHOULD skip the entry and continue reading the file. If the 8th byte is set to 1, the Entry is a non-standard extension. Vendors MAY use this range for vendor-specific data. Filesystem Structure Any Object MUST have a Parent ID and an Object ID. Object ID 0 is reserved for the root directory. File naming conventions Object names MUST NOT contain any type of slash. Object names must also be of the 8.3 format, though the full name MAY be specified with Extended Attributes. Full names in Attributes MUST NOT contain any type of slash. File offsets File offsets are relative to the end of the File Table. Entry Type: File The Entry Specifier byte MUST be F, and the data contained MUST be the name as a string, followed by the file offset and file size represented as an integer, then followed by the Object ID and Parent ID. Entry type: Directory The Entry Specifier byte MUST be D, and the data contained MUST be the name as a string, followed by the Object ID and the Parent ID. Entry type: Extended Attributes The Entry Specifier byte MUST be x, and the data contained MUST be the Object ID of the Entry the Entry is describing, followed by a four byte Attribute and the value. Currently recognized attributes include: NAME: The long name of the Object. PERM: The POSIX-compatible permissions of the Object W32P: Win32-compatible permissions of the Object, which override POSIX permissions. OTIM: Creation time of the Object MTIM: Modification time of the Object CTIM: Metadata update time of the Object ATIM: Access time of the Object Entry type: EOH The Entry Specifier byte MUST be Z, and the data contained MUST be the offset required to reach the end of the file. Compressed URF naming convention In an environment with long names, the file extension SHOULD be urf followed by a period (.) and the compression method (i.e. gz, lzma, xz, deflate) In an environment with 8.3 names, the file extension MUST be one of the following: UMA for LZMA UXZ for XZ UGZ for Gzip UL4 for LZ4 UB2 for BZip2 TODO Document is incomplete. Document should outline how to build the Filesystem structure, etc. Document should be checked for clarity and rewritten if needed.
  2. THIS IS A DRAFT. It may change before becoming "official". Please feel free to suggest breaking changes. Abstract This document provides guidelines for dealing with EEPROMs and locating architecture-specific boot code. Rationale OpenComputers supports a wide variety of architectures. Even more so than in the real world, OpenComputers architectures can differ dramatically from one another. Some architectures run programs in a particular high-level language directly, while others simulate real or fictitious low-level ISAs. Some architectures natively deal with data in 8-bit units, while others have built-in advanced string handling and vector processing capabilities. In contrast with this variety, OpenComputers components have a standard interface. An EEPROM containing boot code can easily end up being used on the "wrong" architecture, to say nothing of boot disks. This standard aims to solve that problem, by providing architecture-aware guidelines for dealing with EEPROMs, and procedures for locating boot code on filesystem-based and sector-based boot media. It aims to be simple to implement on the widest possible variety of architectures. Conventions Unless otherwise specified, all references to text imply 7-bit ASCII codes. Behavior on encountering bytes with the high-bit set is undefined. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. Architecture Identifier Each architecture must provide a unique, preferably meaningful identifier which is specific to that architecture. This is the Architecture Identifier, or AID. The AID SHOULD be the same as the Architecture.Name annotation for the architecture, which is usually the same as the name used in the tooltip of the CPU. An AID MUST contain no bytes other than the following characters: digits, upper and lowercase letters, periods (.), dashes (-), underscores (_), slashes (/), spaces. In addition, an AID MUST NOT begin with a space, end with a space, or contain a run of two or more spaces. An AID SHOULD begin with a capital letter, if for no other reason than to make boot code easier to tell apart from other files and directories in listings. A new AID SHOULD NOT contain spaces, unless it is required for compatibility. An architecture with multiple variants that are mutually incompatible SHOULD use different AIDs for each variant. Fallback schemes, such as one where multiple AIDs are tried, are architecture-specific and outside the scope of this document. CAB-aware EEPROM images ("CABE images") This section applies to architectures, EEPROM flashing utilities, and any hardcoded boot code (analogous to machine.lua in the "standard" Lua architecture). A CAB-aware EEPROM image (a "CABE image") MUST begin with "--[", followed by zero or more "=", followed by "[CABE:". This is the prefix string. A CAB-compliant architecture MUST be prepared to deal with any number of "=" between 0 and 7, and a CABE image SHOULD NOT use more than 7. The prefix string is followed by a single AID. This denotes the "intended architecture" for this CAB image. This is followed by one of two things: A colon (:), in which case the "main body" consists of the bytes following the colon, up until a valid suffix string is encountered. A suffix string, in which case the "main body" consists of the entire remainder of the image, and MUST be valid Lua 5.2 AND Lua 5.3 code. A "suffix string" consists of an ASCII "]", followed by the same number of "=" as were in the prefix string, followed by another "]". In order to be a valid suffix string, it MUST contain precisely the same number of "=" as the prefix string contains. In particular, an otherwise valid suffix string that contains more "=" than the prefix string MUST be treated exactly the same as any other non-suffix-string byte sequence. The "main body" contains the actual EEPROM data for that architecture. The interpretation of this data is architecture-defined. If a CABE image contains data after a valid suffix string, that data MUST be Lua code which is cross-compatible between the Lua 5.2 and 5.3 architectures provided by OpenComputers. If this is not the intended architecture of the CABE image, this code SHOULD consist solely of an informative error call. Any deviation whatsoever from this standard results in a non-CABE image. All handling of non-CABE images is architecture-specific, but a non-CABE image SHOULD be treated however the "main body" of a valid CABE image would be treated. The preferred file extension for CABE images is ".cabe". The preferred MIME type is "application/x-cabe-image", though "application/octet-stream" is acceptable. CABE images MUST NOT be distributed using any "text/*" MIME type, as doing so will almost certainly corrupt binary CABE images. Here is an example CABE image targeting a fictional architecture: --[[CABE:HyperTalk: ask "What is your name?" answer "Hello," && it & "!" ]] error"HyperTalk architecture required" And here is one targeting a built-in Lua architecture: --[[CABE:Lua 5.2]] for n=1,5 do computer.beep(2000, 0.1) end EEPROM-based transparent architecture switching A future OpenComputers release may add support for transparent architecture switching, through additional NBT data for EEPROMs. It is expected that this will consist of a single AID identifying the architecture the EEPROM is designed for. This section applies in the event of such support becoming available. To provide consistency to users, architectures SHOULD NOT attempt to implement any form of automatic architecture switching themselves. An EEPROM flashing utility SHOULD attempt to parse all images as CABE images. If successful, it SHOULD tag the EEPROM appropriately and burn only the "main body". Otherwise, it SHOULD remove any existing architecture tag from the EEPROM and burn the entire image. An architecture booting an EEPROM with a valid architecture tag SHOULD NOT also attempt to parse it as a CABE image. An architecture booting an EEPROM with no valid architecture tag SHOULD attempt to parse it as a CABE image, and MUST NOT affix an architecture tag itself. Boot code This section applies to EEPROMs intended as first-stage bootloaders, as well as programs intended to be booted by such EEPROMs. Bootloaders SHOULD, if the boot EEPROM contains a boot device UUID, attempt to boot from that device first. A boot EEPROM contains a boot device UUID if eeprom.getData() consists entirely of an ASCII UUID, or if it begins with an ASCII UUID followed by a null byte. Managed mode (filesystems) Bootloader behavior on managed filesystems: If "/<AID>" exists and is a directory, boot "/<AID>/boot". If "/<AID>" exists and is a file, boot "/<AID>". Any further cases are architecture-specific. If one of the above conditions are met, but its booting attempt fails, the booting process MUST NOT continue automatically. For instance, if "/<AID>" is a directory but booting "/<AID>/boot" fails, the bootloader MUST either fail with an error, or prompt a user for further action. Exactly what "booting" entails is architecture-specific. On a Lua architecture, it consists of loading a file as Lua code and then executing it. On low-level architectures, it might consist of loading a file's contents to a fixed RAM address and jumping into it. Architectures SHOULD provide a standard way for the first-stage bootloader to tell the booted code the UUID of the filesystem it was loaded from. Example: Consider a boot on the OC-ARM architecture. The bootloader checks if "/OC-ARM" exists. It does exist, and is a directory. The bootloader then attempts to boot "/OC-ARM/boot". It fails, because "/OC-ARM/boot" is not valid. It crashes the machine with an error message explaining the problem. Unmanaged mode (drives) A CAB-compliant bootable disk begins with a boot sector. This boot sector MUST be the first or second sector of the drive. If both the first and second sectors contain a valid boot sector, only the first one will be used. A boot sector begins with the ASCII string "CAB", followed by zero or more text boot records. This list of text records is terminated with an exclamation mark. If this exclamation mark is followed by the particular byte sequence {0x00, 0x1A, 0xCA, 0xBD} (null byte, CP/M end-of-file marker, two-byte magic number), then it is followed by zero or more binary boot records, terminated by a null byte. Boot records MUST NOT extend past the end of the boot sector. Architectures MAY specify that boot records for that architecture must be text or must be binary, and MAY specify that binary boot records must be a particular endianness and/or must be sector-aligned. Bootloaders for architectures that do not specify that boot records must be text or must be binary MUST support both. A text record matches ":<AID>=<offset>+<length>". <AID> is the AID for which the code is intended. <offset> is a decimal number, giving the byte offset at which to begin reading, OR "s" followed by a decimal number, giving the sector number at which to begin reading. <length> is a decimal number giving the number of bytes to read. A binary record is described by the following C99 structure: struct { uint8_t record_length; uint8_t flags; uint16_t load_start; uint32_t load_length; char aid[]; }; record_length is the number that must be added to the offset of this record to skip it. It MUST be equal to 8 + AID length + 1. flags is a bitfield. The following flags are defined: 0x40: If set, load_start is a sector number. If clear, load_start is a byte offset. 0x80: If set, load_start and load_length are little-endian. If clear, load_start and load_length are in network byte order (big-endian). load_start is either a sector number or a byte offset to begin the loading process at. load_length is the number of bytes to read. aid is the AID of the intended architecture, and MUST be null-terminated. As with managed mode, exactly what is done with the loaded data is architecture-specific. Bootloaders that only support binary records should consider a sector to be a valid boot sector if it begins with "CAB", and locate the end of the text boot records without parsing them by searching for the first "!". Bootloaders that only support text records need not consider any bytes past the first null byte. A boot sector that contains no records is valid, and MUST prevent any attempt to read possible subsequent boot sectors. Example 1: CAB:Lua 5.2=s3+17:Lua 5.3=s3+17:HyperTalk=384+5100! (followed directly by binary data:) 001A CABD (valid binary records follow) 0F (the length of the first record) C0 (little-endian, sector offset) 0900 (start at sector number 9) 0000 0100 (load 65536 bytes) 5342 3635 3032 00 (null-terminated string "SB6502") 00 (no more binary records) This drive contains valid boot code for Lua 5.2, Lua 5.3, HyperTalk, and SB6502. Lua 5.2 and 5.3 both use the same boot code, which is 17 bytes long and starts at the beginning of sector number 3. The HyperTalk boot code is 5100 bytes long and starts 384 bytes into the disk, which, when using 256-byte sectors, is halfway through the second sector. The SB6502 boot code is 65536 bytes long and starts at the beginning of sector number 9. Example 2: CAB! This is a valid boot sector, but contains no boot records. This is the safest way to mark a drive as non-bootable.
  3. THIS IS A DRAFT. It may change before becoming "official". Please feel free to suggest breaking changes. Abstract This document provides a binary interchange format, intended primarily to support generic component IO. Rationale OpenComputers' component bus is designed for high-level languages. It sends and receives groups of dynamically typed values. It is intended to be user-friendly and self-discoverable, and it has largely achieved this goal. However, with low-level architectures, there is no obvious, straightforward way to represent these values. This document aims to provide a standard representation, freeing individual architects from having to devise their own representations, and minimizing unnecessary differences between architectures. Every value that can be sent over an OpenComputers bus can be represented as described in this document, and (barring length restrictions) vice versa. Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. All signed integers are two's-complement. Concepts Tag: Gives the type of a subsequent Value. Value: Data whose structure and meaning depend on its type. Tagged Value: A Tag, followed by a Value of the indicated type. Producer: A program or process that generates data in this format. Consumer: A program or process that consumes data in this format. Packed mode: A representation designed to occupy very little space. Unpacked mode: A representation designed to be easy to manipulate on 32-bit architectures. Tags A type tag denotes the type of a subsequent Value. In Packed mode, the tag is a 16-bit signed integer. In Unpacked mode, it is a 32-bit signed integer, aligned to a 4-byte boundary. Values String (UIFTAG_STRING = 0x0000–0x3FFF = 0–16383) A UTF-8 code sequence. The tag provides the length, in bytes, of the sequence. Producers MUST NOT generate invalid code sequences, including "modified UTF-8" conventions such as non-zero NUL and UTF-8 encoded surrogate pairs. Producers MUST NOT arbitrarily prefix strings with a spurious U+FEFF BYTE ORDER MARK. Consumer handling of invalid code sequences is undefined. If a Consumer encounters a String where a Byte Array is expected, the Consumer MAY incur a round-trip conversion to its native string type. This may mean that the bytes the Consumer actually sees differ from the original bytes where invalid code sequences occur. Consumers MUST handle NUL bytes in a String in an appropriate manner. Consumers MUST not assume that Strings are NUL-terminated—they are not. In Unpacked mode, additional zero bytes MUST be added to the end of the String, so that a subsequent Tag will be aligned to a 4-byte boundary. Byte Array (UIFTAG_BYTE_ARRAY = 0x4000-0x7FFF = 16384-32767) An arbitrary sequence of bytes. The tag, minus 16384, provides the length in bytes of the sequence. If a Consumer encounters a Byte Array where a String is expected, the Consumer MUST interpret the Byte Array as if it were a String of the given length. In Unpacked mode, additional zero bytes MUST be added to the end of the Byte Array, so that a subsequent Tag will be aligned to a 4-byte boundary. End (UIFTAG_END = 0x...FFFF = -1) A special tag signifying the end of an Array or Compound. Null (UIFTAG_NULL = 0x...FFFE = -2) Absence of a value. Equivalent to null and nil in various programming languages. (Note: there is no tag -3.) Double (UIFTAG_DOUBLE = 0x...FFFC = -4) A 64-bit IEEE 754 floating point value. Consumers that encounter a Double where an Integer is expected MAY fail. Producers that are producing a Double which has an exact Integer representation SHOULD produce that Integer instead. Integer (UIFTAG_INTEGER = 0x...FFFB = -5) A 32-bit signed integer. Consumers that encounter an Integer where a Double is expected MUST convert the Integer to a Double. Array (UIFTAG_ARRAY = 0x...FFFA = -6) A series of Tagged Values, in a particular order, terminated by an End. Compound (UIFTAG_COMPOUND = 0x...FFF9 = -7) A series of pairs of Tagged Values. The order of the pairs is not significant. Each pair consists of a Key and a Value, in that order. A Key may be any type except a Byte Array, a Null, an Array, or a Compound. A Value may be any type. The list is terminated by an End. If a Consumer encounters an End as the second element of a pair, the result is undefined. UUID (UIFTAG_UUID = 0x...FFF8 = -8) A 128-bit RFC 4122 UUID. Regardless of endianness, the bytes are in display order. Consumers that encounter a UUID where a String is expected MUST convert the UUID to its canonical string representation, in lowercase. Producers and Consumers alike should take note that a random sequence of bytes is not necessarily a valid UUID. True (UIFTAG_TRUE = 0x...FFF7 = -9) A boolean true value. False (UIFTAG_FALSE = 0x...FFF6 = -10) A boolean false value. TODO This document is incomplete. Still to be written: recommendations on endianness and packing, useful common optimizations.
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