config: add `--algorithm` option and documentation.

Doc in `doc/configuration.md` (has to be started sometime, no?).

Configuration function has to be lamely-named set_algo(), because
set_algorithm() is already declared in algorithm.h (prevent namespace
conflict).

algorithm has to be added as global variable due to the way the
callback is done (by CCAN/opt, which in itself is nice).

This can be cleaned up significantly by (at least) introducing a
global configuration struct, but there is no reason to do it now
just for this - better a wholesale manana.

algorithm.c

@@ -17,7 +17,7 @@ typedef struct algorithm_t {
     uint8_t nfactor;  /* N factor (CPU/Memory tradeoff parameter) */
 } algorithm_t;
 
-void set_algorithm(algorithm_t* algo, char* newname) {
+void set_algorithm(algorithm_t* algo, const char* newname) {
     strncpy(algo->name, newname, sizeof(algo->name));
     algo->name[sizeof(algo->name) - 1] = '\0';
 
@@ -28,6 +28,6 @@ void set_algorithm(algorithm_t* algo, char* newname) {
     }
 }
 
-void set_algorithm_nfactor(algorithm_t* algo, uint8_t nfactor) {
+void set_algorithm_nfactor(algorithm_t* algo, const uint8_t nfactor) {
     algo->nfactor = nfactor;
 }

algorithm.h

@@ -9,9 +9,9 @@
 typedef struct algorithm_t algorithm_t;
 
 /* Set default parameters based on name. */
-void set_algorithm(algorithm_t* algo, char* name);
+void set_algorithm(algorithm_t* algo, const char* name);
 
 /* Set to specific N factor. */
-void set_algorithm_nfactor(algorithm_t* algo, uint8_t nfactor);
+void set_algorithm_nfactor(algorithm_t* algo, const uint8_t nfactor);
 
 #endif /* ALGORITHM_H */

doc/configuration.md

@@ -0,0 +1,26 @@
+# Configuration and command-line options
+
+*Work in progress!*
+
+
+## Config-file and CLI options
+
+### algorithm
+
+Allows choosing between the few mining algorithms for incompatible
+cryptocurrencies.
+
+Requires a string.
+
+Currently supported:
+
+* `adaptive-nfactor` - Vertcoin-style adaptive N-factor scrypt.
+N-factor defaults to 11.
+* everything else - Litecoin-style static N-factor scrypt.
+
+
+### nfactor
+
+Overrides the default N-factor scrypt parameter.
+
+Requires an unsigned integer.

miner.h

@@ -1018,6 +1018,8 @@ extern bool fulltest(const unsigned char *hash, const unsigned char *target);
 extern int opt_queue;
 extern int opt_scantime;
 extern int opt_expiry;
+
+extern char* opt_algorithm;
 extern int opt_nfactor;
 
 extern cglock_t control_lock;

sgminer.c

@@ -54,6 +54,8 @@ char *curly = ":D";
 #include "adl.h"
 #include "driver-opencl.h"
 #include "bench_block.h"
+
+#include "algorithm.h"
 #include "scrypt.h"
 
 #if defined(unix) || defined(__APPLE__)
@@ -92,7 +94,11 @@ int opt_log_interval = 5;
 int opt_queue = 1;
 int opt_scantime = 7;
 int opt_expiry = 28;
+
+char* opt_algorithm;
+algorithm_t* algorithm;
 int opt_nfactor = 10;
+
 static const bool opt_time = true;
 unsigned long long global_hashrate;
 unsigned long global_quota_gcd = 1;
@@ -1005,6 +1011,13 @@ static void load_temp_cutoffs()
 	}
 }
 
+static char *set_algo(const char *arg)
+{
+	set_algorithm(algorithm, arg);
+
+	return NULL;
+}
+
 static char *set_api_allow(const char *arg)
 {
 	opt_set_charp(arg, &opt_api_allow);
@@ -1054,6 +1067,9 @@ static char *set_null(const char __maybe_unused *arg)
 
 /* These options are available from config file or commandline */
 static struct opt_table opt_config_table[] = {
+	OPT_WITH_ARG("--algorithm",
+		     set_algo, NULL, NULL,
+		     "Set mining algorithm to most common defaults, default: static"),
 	OPT_WITH_ARG("--api-allow",
 		     set_api_allow, NULL, NULL,
 		     "Allow API access only to the given list of [G:]IP[/Prefix] addresses[/subnets]"),
@@ -1108,7 +1124,7 @@ static struct opt_table opt_config_table[] = {
 #endif
 	OPT_WITH_ARG("--nfactor",
 		     set_int_0_to_9999, opt_show_intval, &opt_nfactor,
-		     "Set scrypt nfactor, default: 10. Currently use 11 for vertcoin!"),
+		     "Set scrypt N-factor parameter, default: 10. Currently use 11 for vertcoin!"),
 	OPT_WITHOUT_ARG("--debug|-D",
 		     enable_debug, &opt_debug,
 		     "Enable debug output"),