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updated with link to script

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10_2_Building_the_Structure_of_P2SH.md
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@ -61,12 +61,35 @@ $ neglehex=$(printf '%x\n' $((0x$lehex | 0x80)))
$ echo $neglehex
9f7b2adc
```
(There's a script at the end to automate all of this.)
### Transform the Hex to Binary
To complete your serialization, you translate the hexcode into binary. On the command line, this just requires a simple invocation of `xxd -r -p`. However, you probably want to do that as part of a a single pipe that will also hash the script ...
## Run The Integer Conversion Script
A complete script for changing an integer between -2147483647 and 2147483647 to a little-endian signed-magnitude representation in hex can be found in th e[src code directory](src/10_2_integer2lehex.sh). You can download it as `integeer2lehex.sh`.
> :warning: **WARNING:** This script has not been robustly checked. If you are going to use it to create real locking scripts you should make sure to double-check and test your results.
Be sure the permissions on the script are right:
```
$ chmod 755 integer2lehex.sh
```
You can then run the script as follows:
```
$ ./integer2lehex.sh 1546288031
Integer: 1546288031
LE Hex: 9f7b2a5c
Length: 4 bytes
Hexcode: 049f7b2a5c
$ ./integer2lehex.sh -1546288031
Integer: -1546288031
LE Hex: 9f7b2adc
Length: 4 bytes
Hexcode: 049f7b2adc
```
## Analyze a P2SH Multisig
To better understand this process, we will reverse-engineer the P2SH multisig that we created in [§6.1: Sending a Transaction to a Multisig](06_1_Sending_a_Transaction_to_a_Multisig.md). Take a look at the `redeemScript` that you used, which you now know is the hex-serialized version of the locking script:
@ -155,72 +178,3 @@ Actually creating the P2SH locking script dives further into the guts of Bitcoin
## What's Next?
Continue "Embedding Bitcoin Scripts" with [§10.3: Running a Bitcoin Script with P2SH](10_3_Running_a_Bitcoin_Script_with_P2SH.md).
## Appendix: The Integer Conversion Script
The following script collects the complete methodology for changing an integer between -2147483647 and 2147483647 to a little-endian signed-magnitude representation in hex:
> :warning: **WARNING:** This script has not been robustly checked. If you are going to use it to create real locking scripts you should make sure to double-check and test your results.
```
file: integer2lehex.sh
#!/bin/bash
if [ -z $1 ];
then
echo "You must include an integer as an argument.";
exit;
fi
if (( $1 > "2147483647" )) || (( $1 < "-2147483647" ));
then
echo "Your number ($1) must be between -2147483647 and 2147483647";
exit;
fi
if [ $1 -lt 0 ];
then
integer=$(echo $((-$1)));
negative=1;
else
integer=$1;
negative=0;
fi
hex=$(printf '%08x\n' $integer | sed 's/^\(00\)*//');
hexfirst=$(echo $hex | cut -c1)
[[ 0x$hexfirst -gt 0x7 ]] && hex="00"$hex
lehex=$(echo $hex | tac -rs .. | echo "$(tr -d '\n')");
if [ "$negative" -eq "1" ];
then
lehex=$(printf '%x\n' $((0x$lehex | 0x80)))
fi
size=$(echo -n $lehex | wc -c | awk '{print $1/2}');
hexcodeprefix=$(printf '%02x\n' $size);
echo "Integer: $1";
echo "LE Hex: $lehex";
echo "Length: $size bytes";
echo "Hexcode: $hexcodeprefix$lehex";
```
Be sure the permissions on the script are right:
```
$ chmod 755 integer2lehex.sh
```
You can then run the script as follows:
```
$ ./integer2lehex.sh 1546288031
Integer: 1546288031
LE Hex: 9f7b2a5c
Length: 4 bytes
Hexcode: 049f7b2a5c
$ ./integer2lehex.sh -1546288031
Integer: -1546288031
LE Hex: 9f7b2adc
Length: 4 bytes
Hexcode: 049f7b2adc
```