├── .circleci
    └── config.yml
├── .gitignore
├── Makefile
├── README.md
└── main.c


/.circleci/config.yml:
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 1 | version: 2
 2 | 
 3 | workflows:
 4 |   version: 2
 5 |   compile:
 6 |     jobs:
 7 |       - build
 8 | 
 9 | jobs:
10 |   build:
11 |     docker:
12 |       - image: gcc:8.2
13 |     steps:
14 |       - checkout
15 |       - run: make slice
16 | 


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/.gitignore:
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1 | .vscode/
2 | .DS_Store
3 | slice
4 | 


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/Makefile:
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 1 | CC ?= clang
 2 | 
 3 | .PHONY: all install uninstall clean
 4 | 
 5 | all: slice
 6 | 
 7 | slice: main.c
 8 | 	$(CC) main.c -std=c99 -o slice -Wall -Wextra -O3
 9 | 
10 | install: slice
11 | 	cp slice /usr/local/bin/slice
12 | 
13 | uninstall:
14 | 	rm -f /usr/local/bin/slice
15 | 
16 | clean:
17 | 	rm -f slice
18 | 


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/README.md:
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 1 | # 🍕 slice
 2 | 
 3 | A no-nonsense tool to copy a blob of data from one file to another.
 4 | 
 5 | Opens `input`, seeks to `start`, reads `length` bytes, and writes them to `output`.
 6 | 
 7 | ## Options
 8 | 
 9 | ```
10 | -i,--input <input>
11 | 	Source file path to read from.
12 | 	[required]
13 | 
14 | -o,--output <output>
15 | 	Destination file path to write to.
16 | 	[required]
17 | 
18 | -s,--start <start>
19 | 	Start offset in bytes.
20 | 	[optional, defaults to 0 if omitted]
21 | 
22 | -n,--length <length>
23 | 	Length of data to copy, in bytes.
24 | 	[optional, reads to the end of input if omitted]
25 | ```
26 | 
27 | ## Building
28 | 
29 | On any \*nix system it _should_ be as simple as:
30 | 
31 | ```
32 | git clone https://github.com/lunasorcery/slice.git
33 | cd slice
34 | make slice && make install
35 | ```
36 | 
37 | This depends on a C compiler being available. If you encounter issues, please let me know.
38 | 


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/main.c:
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  1 | #include <stdio.h>
  2 | #include <stdint.h>
  3 | #include <stdbool.h> /* how is this not a language feature? !*/
  4 | #include <stdlib.h>
  5 | #include <getopt.h>
  6 | 
  7 | #define eprintf(...) fprintf(stderr, __VA_ARGS__)
  8 | 
  9 | /* save ourselves an include */
 10 | int64_t min(int64_t a, int64_t b) { return a < b ? a : b; }
 11 | 
 12 | int main(int argc, char** argv)
 13 | {
 14 | 	int const BUFFER_SIZE = 1024*1024;
 15 | 
 16 | 	char const* pathIn = NULL;
 17 | 	char const* pathOut = NULL;
 18 | 	int64_t start = 0;
 19 | 	int64_t length = 0;
 20 | 	bool readToEnd = true;
 21 | 
 22 | 	while (1)
 23 | 	{
 24 | 		static struct option long_options[] = {
 25 | 			{ "input",  required_argument, 0, 'i' },
 26 | 			{ "output", required_argument, 0, 'o' },
 27 | 			{ "start",  required_argument, 0, 's' },
 28 | 			{ "length", required_argument, 0, 'n' },
 29 | 			{ 0, 0, 0, 0 }
 30 | 		};
 31 | 
 32 | 		int option_index = 0;
 33 | 		int c = getopt_long(argc, argv, "i:o:s:n:", long_options, &option_index);
 34 | 		
 35 | 		if (c == -1) {
 36 | 			break;
 37 | 		}
 38 | 
 39 | 		switch (c) {
 40 | 			case 'i': {
 41 | 				pathIn = optarg;
 42 | 				break;
 43 | 			}
 44 | 			case 'o': {
 45 | 				pathOut = optarg;
 46 | 				break;
 47 | 			}
 48 | 			case 's': {
 49 | 				start = strtol(optarg, NULL, 10);
 50 | 				if (start < 0) {
 51 | 					eprintf("Start offset must be greater than or equal to zero.\n");
 52 | 					return 1;
 53 | 				}
 54 | 				break;
 55 | 			}
 56 | 			case 'n': {
 57 | 				length = strtol(optarg, NULL, 10);
 58 | 				if (length <= 0) {
 59 | 					eprintf("Length must be greater than zero.\n");
 60 | 					return 1;
 61 | 				}
 62 | 				readToEnd = false;
 63 | 				break;
 64 | 			}
 65 | 		}
 66 | 	}
 67 | 
 68 | 	if (!pathIn || !pathOut)
 69 | 	{
 70 | 		eprintf("usage:\n");
 71 | 		eprintf("slice -i <infile> -o <outfile> -s <start offset> -n <length>\n");
 72 | 		return 1;
 73 | 	}
 74 | 
 75 | 	FILE* fhIn = fopen(pathIn, "rb");
 76 | 	if (!fhIn)
 77 | 	{
 78 | 		eprintf("Failed to open '%s' for reading.\n", pathIn);
 79 | 		return 1;
 80 | 	}
 81 | 
 82 | 	FILE* fhOut = fopen(pathOut, "wb");
 83 | 	if (!fhOut)
 84 | 	{
 85 | 		eprintf("Failed to open '%s' for writing.\n", pathOut);
 86 | 		return 1;
 87 | 	}
 88 | 
 89 | 	fseek(fhIn, start, SEEK_SET);
 90 | 
 91 | 	unsigned char buffer[BUFFER_SIZE];
 92 | 
 93 | 	int64_t totalBytesCopied = 0;
 94 | 	if (readToEnd)
 95 | 	{
 96 | 		int64_t bytesRead;
 97 | 		do {
 98 | 			bytesRead = fread(buffer, 1, BUFFER_SIZE, fhIn);
 99 | 			if (bytesRead > 0)
100 | 			{
101 | 				fwrite(buffer, 1, bytesRead, fhOut);
102 | 				totalBytesCopied += bytesRead;
103 | 			}
104 | 		} while (bytesRead != 0);
105 | 
106 | 		printf(
107 | 			"Copied %lld bytes from '%s'+0x%llx to '%s'\n",
108 | 			totalBytesCopied,
109 | 			pathIn,
110 | 			start,
111 | 			pathOut
112 | 		);
113 | 	}
114 | 	else
115 | 	{
116 | 		while (totalBytesCopied < length)
117 | 		{
118 | 			int64_t const bytesRead = fread(buffer, 1, BUFFER_SIZE, fhIn);
119 | 			if (bytesRead > 0)
120 | 			{
121 | 				int64_t const bytesToWrite = min(length - totalBytesCopied, bytesRead);
122 | 				fwrite(buffer, 1, bytesToWrite, fhOut);
123 | 				totalBytesCopied += bytesToWrite;
124 | 			}
125 | 			else
126 | 			{
127 | 				break;
128 | 			}
129 | 		}
130 | 
131 | 		if (totalBytesCopied == length)
132 | 		{
133 | 			printf(
134 | 				"Copied %lld bytes from '%s'+0x%llx to '%s'\n",
135 | 				totalBytesCopied,
136 | 				pathIn,
137 | 				start,
138 | 				pathOut
139 | 			);
140 | 		}
141 | 		else
142 | 		{
143 | 			if (totalBytesCopied == 0)
144 | 			{
145 | 				eprintf(
146 | 					"Attempted to copy %lld bytes from '%s'+0x%llx to '%s', but no data was available.\n",
147 | 					length,
148 | 					pathIn,
149 | 					start,
150 | 					pathOut
151 | 				);
152 | 			}
153 | 			else
154 | 			{
155 | 				eprintf(
156 | 					"Attempted to copy %lld bytes from '%s'+0x%llx to '%s', but only %lld %s available.\n",
157 | 					length,
158 | 					pathIn,
159 | 					start,
160 | 					pathOut,
161 | 					totalBytesCopied,
162 | 					totalBytesCopied == 1 ? "byte was" : "bytes were"
163 | 				);
164 | 			}
165 | 			fclose(fhIn);
166 | 			fclose(fhOut);
167 | 			return 1;
168 | 		}
169 | 	}
170 | 
171 | 	fclose(fhIn);
172 | 	fclose(fhOut);
173 | }
174 | 


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