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Questions tagged [endianness]

Endianness refers to how multi-byte values are stored in memory, sent between devices or stored on disk. "Big-Endian" values are stored with their most-significant byte first, and "Little-Endian" values are stored with their least-significant byte first. Other byte-orders are possible but very uncommon, and cannot be described this way.

Endianness is the organization and ordering of byte values in multi-byte words. There are two main forms of endianness: big-endian and little-endian.

Big endian (BE) means that the most significant bits are stored first (lowest address). It is similar to reading or saying the name of a decimal number in reading order.

Little endian (LE) means that the least significant bits are stored first. The bytes are stored in reverse of the big-endian format.

There are other forms of byte orderings, but they are rare. They may also be called mixed-endian.

Usage of endianness

When we talk about endian, we often refer to the endianness of an instruction architecture/CPU or the endianness of a file. The endianness of an architecture or a CPU is how the processor organizes the bits in a multi-byte word.

  • Motorola 68000 is a big-endian architecture. It stores multi-byte words in big-endian ordering.
  • Intel processors and the x86 architecture are little-endian.
  • MIPS can run in both big-endian and little-endian format, and you can select the endianness. MIPS is a Bi-endian format.

The endianness of a file indicates how the bytes of a multi-byte word is ordered in a given file (applies both to binary and text files). Sometimes, we indicate the endianness of a file by putting a byte-order mark (BOM) as the first byte of that file.

  • A big-endian UTF-16 text file with BOM would begin with the two bytes FE FF and have all the two-byte characters (each surrogate in a surrogate pair is also one character) be expressed in big endian.
  • A little-endian UTF-16 text file with BOM would begin with the two bytes FF FE and have all the two-byte characters be expressed in little endian.

Examples of endianness

A 32-bit signed int value, 12356789 is stored as four bytes in two's complement format.

  • In big endian, the value is stored as 07 5B CD 15 in hexadecimal notation.
  • In little endian, the value is stored as 15 CD 58 07 in hexadecmial notation.

A UTF-16 text file with BOM contains these characters: A 汉.

  • The BOM character has value U+FEFF. The emoji has Unicode value U+1F197 is expressed as two surrogate pairs, U+D83C U+DD97
  • In big endian, the characters are stored as FEFF 0041 0020 6C49 D83C DD97
  • In little endian, they are stored as FFFE 4100 2000 496C 3CD8 97DD

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How is UTF-16 with big endian BOM (FEFF) stored in a little endian machine?

From my understanding, the endianness of UTF-16 is independent from the endianness of the host architecture. Let's take the character 0x0042 (the letter "D") saved in a file for example. In big endian UTF-16 (UTF-16BE) file format, it'll be encoded…
user1968919
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Moving binary files between big endian and little endian platforms

I know that network byte order is big endian regardless of host endianness. My question is what happens when a binary file is moved from a BE to LE platform. From this post I can see the data byte order on disk is the same as memory byte order of…
Dan
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When would endianness be an issue when hashing data?

I am studying the SHA256 hash algorithm, which uses big-endian byte order. Would I actually ever have to consider endianness when using hashing algorithms? Maybe when a different endian computer runs my script?
Mackenzie Moore
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C++ memory endiannes under question for me

For example, I have an array of 512 bytes called blocks_data, I create an unsigned long long pointer, which points to the 512 - 8 = 508 byte in the array. I dereference the pointer and assign a value, let it be 3. As I know, Intel x86_64 uses…
Sarnaif Channel
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Javabuffer returns symbols

I would like to read packet payload from dump, but the problem is, that when I calls .toString() it returns a symbols. Using this lib https://github.com/aboutsip/pkts import io.pkts.PacketHandler; import io.pkts.buffer.Buffer; import…
fauzt
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Create a 16 Bit TIFF image from a Python string

I need to use scanner in 16 bit depth and color mode, so i modified python-imaging-sane (that doesn't support RGB tiff with 16 bit depth) to receive from a scanner (epson v500) an image in a Python string. this is the modified function that i use to…
ilmioalias
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How to query target architecture endianness during gcc compilation?

I would like to promote more of my endianness logic to compile time constexpr's. I know that in C++20, this is highly standardized via std::endian. However, for the moment I am targeting C++17. How can I query the target architecture's endianness…
mcandre
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Hex to dec conversion but little endian python

u16ModuleID_hex = f3.read(4) u16ModuleID_dec = int(u16ModuleID_hex, 16) This is how I converted hex to dec, but it turned out to be in big endian and I need little endian. I tried to use struct function but I get some problem,…
immonual
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stack vs .data grow size matters?

I am a little bit confused with memory addresses. I know that stack grows towards lower addresses and that .data section grows towards higher addresses. Let's say I want to save 0x1234 in address 0x100. if 0x100 is in stack then 0x100 takes 34 and…
john
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Do I need to care about endianness when creating c++ program?

I know that i should care about this when reading data from binary files and with networking but what with a source code? Does it matter for endianness if I assign value, for example int = 42? Will it compile on big endian machine with big endian…
zix527
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Does Endian-ness affect the union members when they are integers?

union Chunk { struct { uint32_t index, total; } m_; uint64_t m_PlaceHolder; } chunk; chunk.m_.index = 1; chunk.m_.total = 2; SendOverTCPNetwork(chunk.m_PlaceHolder); // different platform OS will receive this A union member is set for 2…
iammilind
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convert hex to float32_LE

I hope you and your family are well. I am getting difficulty in convert hex to float32_LE. I tried some different online JavaScript editors but not working well. If someone has an idea how can find the best resources to convert hex to float32_LE. I…
stuai
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Which bit numbering is used by big-endian ARM: "MSB 0" or "LSB 0"?

Which bit numbering is used by big-endian ARM (ex. ARMv4, ARMv5, ARMv6): MSB 0 or LSB 0? Please, provide a source.
pmor
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Is there an architecture-independent method to create a little-endian byte stream from a value in C?

I am trying to transmit values between architectures, by creating a uint8_t[] buffer and then sending that. To ensure they are transmitted correctly, the spec is to convert all values to little-endian as they go into the buffer. I read this article…
Mitch Ostler
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In what cases do I need to consider byte order?

Do I need to consider endianness when serializing/deserializing data to write/read binary to/from the same machine? There's no network communication involved.
Attis
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