decodes UTF-8 text into codepoints
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commit 44b48a9b24e3dda0688b28e9dffded005a9d1d3d
Author: David DiPaola <>
Date:   Thu, 27 Dec 2018 13:28:16 -0500

initial commit

A.gitignore | 4++++
ALICENSE | 117+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
AMakefile | 15+++++++++++++++
AREADME | 10++++++++++
Amain.c | 75+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 221 insertions(+), 0 deletions(-)

diff --git a/.gitignore b/.gitignore @@ -0,0 +1,4 @@ +utf8_decode + +.*.swp + diff --git a/LICENSE b/LICENSE @@ -0,0 +1,117 @@ +CC0 1.0 Universal + +Statement of Purpose + +The laws of most jurisdictions throughout the world automatically confer +exclusive Copyright and Related Rights (defined below) upon the creator and +subsequent owner(s) (each and all, an "owner") of an original work of +authorship and/or a database (each, a "Work"). + +Certain owners wish to permanently relinquish those rights to a Work for the +purpose of contributing to a commons of creative, cultural and scientific +works ("Commons") that the public can reliably and without fear of later +claims of infringement build upon, modify, incorporate in other works, reuse +and redistribute as freely as possible in any form whatsoever and for any +purposes, including without limitation commercial purposes. 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Affirmer understands and acknowledges that Creative Commons is not a + party to this document and has no duty or obligation with respect to this + CC0 or use of the Work. + +For more information, please see +<> + diff --git a/Makefile b/Makefile @@ -0,0 +1,15 @@ +#2018 David DiPaola +#licensed under CC0 (public domain, see + +BIN = utf8_decode + +.PHONY: all +all: $(BIN) + +$(BIN): main.c + $(CC) -Wall -Wextra -O2 $(CFLAGS) $< -o $@ + +.PHONY: clean +clean: + rm -rf $(BIN) + diff --git a/README b/README @@ -0,0 +1,10 @@ +# nix_utf8_decode +decodes UTF-8 text into codepoints + +## usage +`echo -n 'abc ¢ह€𐍈' | utf8_decode` + +## building and installing + - build: `make` + - install: `sudo cp utf8_decode /usr/local/bin/` + diff --git a/main.c b/main.c @@ -0,0 +1,75 @@ +/* +2018 David DiPaola +licensed under CC0 (public domain, see +*/ + +#include <unistd.h> + +#include <stdio.h> + +static void +_print_codepoint(unsigned int codepoint) { + if (codepoint <= 0xFFFF) { + printf("U+%04X" "\n", codepoint); + } + else if (codepoint <= 0xFFFFF) { + printf("U+%05X" "\n", codepoint); + } + else if (codepoint <= 0x10FFFF) { + printf("U+%06X" "\n", codepoint); + } +} + +int +main() { + unsigned char byte; + unsigned int remaining = 0; + unsigned int codepoint = 0; + size_t offset = 0; + while (read(STDIN_FILENO, &byte, sizeof(byte)) == sizeof(byte)) { + if (remaining == 0) { + if (byte <= 0x7F) { + _print_codepoint(byte); + codepoint = 0; + remaining = 0; + } + else if (((byte >> 5) & 0b111) == 0b110) { + codepoint = byte & 0b11111; + remaining = 1; + } + else if (((byte >> 4) & 0b1111) == 0b1110) { + codepoint = byte & 0b1111; + remaining = 2; + } + else if (((byte >> 3) & 0b11111) == 0b11110) { + codepoint = byte & 0b111; + remaining = 3; + } + else { + fprintf(stderr, "ERROR at offset 0x%zX: invalid start byte: 0x%02X" "\n", offset, byte); + codepoint = 0; + remaining = 0; + } + } + else { + if (((byte >> 6) & 0b11) == 0b10) { + codepoint = (codepoint << 6) | (byte & 0b111111); + remaining--; + + if (remaining == 0) { + _print_codepoint(codepoint); + } + } + else { + fprintf(stderr, "ERROR at offset 0x%zX: invalid continuation byte: 0x%02X" "\n", offset, byte); + codepoint = 0; + remaining = 0; + } + } + + offset++; + } + + return 0; +} +