Can't navigate through a file using fseek (C) -


i'm trying navigate through file until find 2 rows first 4 digits of first different first 4 of next one. i've been using fseek navigate trough until find sequence want. it's list of population decade, , each decade there more 1 line, in sequence, oldest newest year. , use ftell in main first offset can start reading in middle of file.

the problem here keeps going backwards when offset positive , should forwards.

the lines should make go forward this:

encontrar_inicio(f, ano, offset/2);

and shows:

1980 é maior que 1950 ano maior, anda para frente 1980 é maior que 1910 ano maior, anda para frente 1980 é maior que 1900 ano maior, anda para frente 1980 é maior que 1880 ano maior, anda para frente 1980 é maior que 1860 ano maior, anda para frente

it says 1980 bigger [year], go forward. doesn't. , after printf gives line line i've posted above.

and whole function:

void encontrar_inicio (file *f, int ano, long int offset) {     int i, meio, ano2;     char aux[100], aux2[100], aux3[100], lixo[100];      //printf("%lu\n", offset);     fseek( f, offset, seek_set);      fgets(aux, 100, f);      fgets(aux2, 5, f);      ano2 = atoi(aux2);      if(ano==ano2)     {         printf("%d é igual %d anos iguais, anda para trás\n", ano, ano2);         encontrar_inicio(f, ano, -offset/2);//go in file     }     if(ano != ano2)     {   if(ano < ano2)         {             printf("%d é menor q %d ano menor, anda para trás\n", ano, ano2);             encontrar_inicio(f, ano, -offset/2);//go in file         }         if(ano > ano2)         {             printf("aqui\n");             fgets(lixo, 100, f);//next line             fgets(aux3, 5, f);             int ano3 = atoi(aux3);               if(ano==ano3)             {                 printf("%d é igual %d encontrou o ano, começa ler\n", ano, ano3);                 return;                 //começa ler             }             if(ano!=ano3)             {                 printf("%d é maior que %d ano maior, anda para frente\n", ano, ano3);                 encontrar_inicio(f, ano, offset/2); //go forward in file              }          }     } }

i've been changing couple of things can't further this. appreciated.

i apologise if there wrong question it's first one.

the file reads (with decades in middle):

year,age,marst,sex,people 1850,0,0,1,1483789 1850,0,0,2,1450376 1850,5,0,1,1411067 2000,90,4,2,29292 2000,90,5,1,147615 2000,90,5,2,774069 2000,90,6,1,15627 2000,90,6,2,59113

edit - ended doing this, , it's working charm.

void encontrar_inicio (file *f, int ano, long offsetmin, long offsetmax) {     int ano2;     char aux[100], aux2[200], aux3[100], *aux4, lixo[100], lixo2[100];     long meio;      meio = (offsetmin+offsetmax)/2;      int anoinicio = inicio_ficheiro_ano(f);      if(ano==anoinicio)     {         printf("%d igual %d, começar ler", ano, anoinicio);         //inserir dados em;         return;     }      fseek( f, meio, seek_set);      fgets(aux, 100, f);      fgets(aux2, 200, f);      aux4 = strtok(aux2, ",");      ano2 = atoi(aux4);      if(ano==ano2)     {         printf("%d é igual %d anos iguais, anda para trás\n", ano, ano2);         //return;         encontrar_inicio(f, ano, offsetmin, meio);//go in file     }     if(ano != ano2)     {   if(ano < ano2)         {             printf("%d é menor q %d ano menor, anda para trás\n", ano, ano2);             //return;             encontrar_inicio(f, ano, offsetmin, meio);//go in file         }         if(ano > ano2)         {             fgets(lixo, 100, f);//next line             fgets(aux3, 5, f);             int ano3 = atoi(aux3);              if(ano==ano3)             {                 printf("%d é igual %d encontrou o ano, começa ler\n", ano, ano3);                 fseek(f, -strlen(aux2), seek_cur);                 return;                 //começa ler             }             if(ano!=ano3)             {                 printf("%d é maior que %d ano maior, anda para frente\n", ano, ano3);                 encontrar_inicio(f, ano, meio, offsetmax); //go forward in file              }          }     } }

you might want try change first encontrar_inicio with:

encontrar_inicio(f, ano, offset/2);

(your version using negative offset)

and on second with:

encontrar_inicio(f, ano, offset + ((maxoffset - offset)/2));

(your version going back, instead of going forward. offset greater offset/2)


Comments

Post a Comment

Popular posts from this blog

python - How to create a legend for 3D bar in matplotlib? -

Image
given ax = plt.subplot() : ax.bar()[0] can passed plt.legend() . however, ax.bar3d() returns none . how create legend displayed bars? update: passing legend="stuff" ax.bar3d() , calling ax.legend() raises /usr/lib/python2.6/site-packages/matplotlib/axes.py:4368: userwarning: no labeled objects found. use label='...' kwarg on individual plots. warnings.warn("no labeled objects found. " you need use proxy artist legends not supported. this code: from mpl_toolkits.mplot3d import axes3d import matplotlib.pyplot plt import numpy np fig = plt.figure() ax = fig.add_subplot(111, projection='3d') x, y = np.random.rand(2, 100) * 4 hist, xedges, yedges = np.histogram2d(x, y, bins=4) elements = (len(xedges) - 1) * (len(yedges) - 1) xpos, ypos = np.meshgrid(xedges[:-1]+0.25, yedges[:-1]+0.25) xpos = xpos.flatten() ypos = ypos.flatten() zpos = np.zeros(elements) dx = 0.5 * np.ones_like(zpos) dy = dx.copy() dz = hist.flatten() ax...
Read more

java - Multi-Label Document Classification -

i have database in store data based upon following 3 fields: id, text, {labels}. note each text has been assigned more 1 label \ tag \ class. want build model (weka \ rapidminer \ mahout) able recommend \ classify bunch of labels \ tags \ classes given text. i have heard svm , naive bayes classifier, not sure whether support multi-label classification or not. guides me right direction more welcome! the basic multilabel classification method one-vs.-the-rest (ovr), called binary relevance (br). basic idea take off-the-shelf binary classifier, such naive bayes or svm, create k instances of solve k independent classification problems. in python-like pseudocode: for each class k: learner = svm(settings) # example labels = [class_of(x) == k x in samples] learner.learn(samples, labels) then @ prediction time, run each of binary classifiers on sample , collect labels predict positive. (both training , prediction can done in parallel, since problems assumed ...
Read more

php - Dynamic url re-writing using htaccess -

how can rewrite http://mydomain.com/test/master.php?catid=2&subcatid=8 http://mydomain.com/test/master.php/catname/subcat using .htaccess file. once rewritten, how can access these parameters in master.php? note: untested, let me know if doesn't work. rewriterule ^master.php/([a-za-z0-9_-]+)/([a-za-z0-9_-]+)$ /master.php?catid$1&subcatid=$2 [l]
Read more