function - can someone explain this short segment of C++ code, I can't make heads or tails of it - 


#include <opcodes.h> const char *getopcodename(     uint8_t op ) {     #define opcode(x, y) if((0x##y)==op) return "op_" #x;         opcodes     #undef opcode     return "op_unknown"; }

link code here: https://github.com/znort987/blockparser/blob/master/opcodes.cpp

here link included opcodes.h

i understand strangely formatted function, however, wondering * @ beginning of function name means. assume has pointers?

also, how #undef , #define statements valid? there's no semicolon after either one, , 1 of them seems defined one-line function. (0x##y) mean? return "op_" #x mean? haven't ever come across syntax before.

i want c++ more seriously, it's hard when looking @ code tell going on. how can learn syntax , rules effectively?

run code thru c++ preprocessor, e.g. using g++ -wall -c -e opcodes.cpp > opcodes.i inside generated opcodes.i

#define not statement preprocessor directive.

the macro opcodes gets expanded big chunk, notably containing opcode( nop, 61) expanded 

if ((0x61)==op) return "op_" "nop";

the 2 string literals concatenated one, "op_nop" here.

gcc has documentation on cpp preprocessor. read stringification (with single # ending #x; of opcode macro) , concatenation (with double ## (0x##y) of opcode macro).


Comments

Post a Comment

Popular posts from this blog

php - Add the correct number of days for each month -

using following function can display years , months between 2 dates, how can add correct days each month array within each month? can't add days manually need account leap years etc. function yearmonth($start_date, $end_date) { $begin = new datetime( $start_date ); $end = new datetime( $end_date); $interval = new dateinterval('p1m'); // 1 month interval $period = new dateperiod($begin, $interval, $end); foreach ( $period $dt ) $years[$dt->format( "y" )][] = $dt->format( "f" ); return $years; } $list = yearmonth("2007-03-24", "2009-06-26"); var_dump($list); since nobody else answered: function yearmonth($start_date, $end_date) { $begin = new datetime( $start_date ); $end = new datetime( $end_date); $interval = new dateinterval('p1d'); // 1 month interval $period = new dateperiod($begin, $interval, $end); $lastmonth = null; $lastyear = null; $aresult = array(); forea...
Read more

java.util.scanner - How to read and add only numbers to array from a text file -

i'm learning java , have question regarding reading file want read numbers file contains strings well. here example of file: 66.56 "3 java 3-43 5-42 2.1 1 and here coding: public class test { public static void main (string [] args){ if (0 < args.length) { file x = new file(args[0]); try{ scanner in = new scanner( new fileinputstream(x)); arraylist<double> test = new arraylist<>(); while(in.hasnext()){ if(in.hasnextdouble()){ double f=in.nextdouble(); test.add(f);} else {in.next();} } catch(ioexception e) { system.err.println("exception during reading: " + e); } } my problem add 66.56,2.1 , 1 doesn't add 3 after "3 or ignores 3-43 , 5-42 can tell me how skip strings , add doubles here? thanks all said 3 ie; "3, 3-43 , 4-42 strings either u read string , split , check number @ " , - or put in space between characters , integers. jvm after compilation tre...
Read more